Author: S.S. Narwal
Publisher: Scientific Publishers
ISBN: 9387913740
Category : Technology & Engineering
Languages : en
Pages : 310
Book Description
This volume has 11 Chapters, divided in three Sections viz., Entomology, Nematology and Weeds. It provides complete information about the various techniques used for Allelopathy Research in the field of Entomology, Nematology and Weeds. It is written in a simple and lucid language. It will be very useful to undergraduate and Post graduate students and Faculty for used in Class room and Laboratory experiments and research. We are thankful to Prof. G. S. Dhaliwal, Department of Entomology, Punjab Agricultural University, Ludhiana and Prof. V. Mojumder, Division of Nematology, Indian Agricultural Research Institute, New Delhi for Peer Review of Entomology and Nematology Manuscripts.
Research Methods in Plant Sciences: Allelopathy Vol.2(Plant Protection)
Author: S.S. Narwal
Publisher: Scientific Publishers
ISBN: 9387913740
Category : Technology & Engineering
Languages : en
Pages : 310
Book Description
This volume has 11 Chapters, divided in three Sections viz., Entomology, Nematology and Weeds. It provides complete information about the various techniques used for Allelopathy Research in the field of Entomology, Nematology and Weeds. It is written in a simple and lucid language. It will be very useful to undergraduate and Post graduate students and Faculty for used in Class room and Laboratory experiments and research. We are thankful to Prof. G. S. Dhaliwal, Department of Entomology, Punjab Agricultural University, Ludhiana and Prof. V. Mojumder, Division of Nematology, Indian Agricultural Research Institute, New Delhi for Peer Review of Entomology and Nematology Manuscripts.
Publisher: Scientific Publishers
ISBN: 9387913740
Category : Technology & Engineering
Languages : en
Pages : 310
Book Description
This volume has 11 Chapters, divided in three Sections viz., Entomology, Nematology and Weeds. It provides complete information about the various techniques used for Allelopathy Research in the field of Entomology, Nematology and Weeds. It is written in a simple and lucid language. It will be very useful to undergraduate and Post graduate students and Faculty for used in Class room and Laboratory experiments and research. We are thankful to Prof. G. S. Dhaliwal, Department of Entomology, Punjab Agricultural University, Ludhiana and Prof. V. Mojumder, Division of Nematology, Indian Agricultural Research Institute, New Delhi for Peer Review of Entomology and Nematology Manuscripts.
Allelopathy in Crop Production
Author: S.S. Narwal
Publisher: Scientific Publishers
ISBN: 9387741109
Category : Technology & Engineering
Languages : en
Pages : 320
Book Description
Allelopathy offers great potential: (a) to increase agriculture production (food grains, vegetables, fruits, forestry), (b) to decrease harmful effects of modern agricultural practices (multiple cropping, leaching losses from N – fertilizers, indiscriminate use of pesticides viz. weedicides, fungicides, insecticides and nematicides and development of pesticides tolerant /resistant biotypes in pests) on soil health/productivity and on environment and (c) to maintain soil productivity and pollution free environment for our future generations. It is hoped that in the near future the allelopathy may be used in crop production, crop protection, agroforestry and agro-horticultural systems of developed countries. Therefore, it may be one of the strategies to increase agricultural production in Sustainable Agriculture of 21st century. This book is based on the research findings and addresses to various intricate problems of crop production, to which there was no definite answer in the past but now have been attributed to allelopathy.
Publisher: Scientific Publishers
ISBN: 9387741109
Category : Technology & Engineering
Languages : en
Pages : 320
Book Description
Allelopathy offers great potential: (a) to increase agriculture production (food grains, vegetables, fruits, forestry), (b) to decrease harmful effects of modern agricultural practices (multiple cropping, leaching losses from N – fertilizers, indiscriminate use of pesticides viz. weedicides, fungicides, insecticides and nematicides and development of pesticides tolerant /resistant biotypes in pests) on soil health/productivity and on environment and (c) to maintain soil productivity and pollution free environment for our future generations. It is hoped that in the near future the allelopathy may be used in crop production, crop protection, agroforestry and agro-horticultural systems of developed countries. Therefore, it may be one of the strategies to increase agricultural production in Sustainable Agriculture of 21st century. This book is based on the research findings and addresses to various intricate problems of crop production, to which there was no definite answer in the past but now have been attributed to allelopathy.
Handbook of Practical Nematology
Author: D.C. Gupta
Publisher: Scientific Publishers
ISBN: 9387869180
Category : Technology & Engineering
Languages : en
Pages : 162
Book Description
Nematology is the discipline of science that deals with the study of nematodes or roundworms. Current requirements of practical nematological work and unavailability of expertise and studies in this field indicate a dire need to encourage the likes of this book on the neglected groups of organisms. The authors, in the present book, have attempted to cover the practical aspects of Nematology for U.G. and P.G. students, teachers and research workers. Rather than enlisting numerous methods adopted by various workers, an emphasis is given to most commonly used techniques for every exercise. Additionally, to gain in depth knowledge on a particular topic, further readings have been suggested at the end of each exercise. Illustrations have also been given that will help the readers in the identification of common nematode species and disease symptoms caused by them.
Publisher: Scientific Publishers
ISBN: 9387869180
Category : Technology & Engineering
Languages : en
Pages : 162
Book Description
Nematology is the discipline of science that deals with the study of nematodes or roundworms. Current requirements of practical nematological work and unavailability of expertise and studies in this field indicate a dire need to encourage the likes of this book on the neglected groups of organisms. The authors, in the present book, have attempted to cover the practical aspects of Nematology for U.G. and P.G. students, teachers and research workers. Rather than enlisting numerous methods adopted by various workers, an emphasis is given to most commonly used techniques for every exercise. Additionally, to gain in depth knowledge on a particular topic, further readings have been suggested at the end of each exercise. Illustrations have also been given that will help the readers in the identification of common nematode species and disease symptoms caused by them.
Research Methods in Plant Sciences: Allelopathy Vol.1(Soil Analysis)
Author: S.S. Narwal
Publisher: Scientific Publishers
ISBN: 938804312X
Category : Technology & Engineering
Languages : en
Pages : 375
Book Description
Allelopathy is a new field of science, as the term 'Allelopathy' was coined by Prof. Hans Molisch, a German Plant Physiologist in 1937. Till now lot of Allelopathy research work has been done in various fields of Agricultural and Plant Sciences. However, there is no compilation of various Research Methods used. Every scientist is conducting research in his own way. It is causing lot of problems to researchers working in underdeveloped/Third World Countries in small towns without Library facilities. Therefore, to make available the standard methods for conducting allelopathy research independently, this multi-volume book has been planned. Since allelopathy is multi-disciplinary area of research, hence, volumes have been planned for each discipline. Prof. S.S. Narwal has planned this multi-volume Book Research Methods in Plant Sciences: Allelopahty. Three volumes (Volume 1. Soil Analysis, Volume 2. Plant Protection and Volume 3. Plant Pathogens) of this Book have been released during the IV. International Allelopathy Conference, 2004 at Hisar(India). Five volumes (Volume 4. Plant Analysis, Volume 5. Physiological Processes, Volume 6. Biochemical Processes, Volume 7. Forestry/Agroforestry Research and Volume 8. Isolation, Identification and Characterization of allelochemicals are under preparation. Volume 1. Soil Analysis is consists of 20 Chapters, describing the methods to analyse various types of soil properties. The Book is devided into three Sections: General, Physio-chemical properties and Soil microbiology. It provides complete information for Soil Analysis in simple and lucid language. The Figures/ illustrations have been given at appropriate places in text. It will prove very useful to undergraduate and post graduate students and teaching Faculty for Class Room and Laboratory experiments as well as for research.
Publisher: Scientific Publishers
ISBN: 938804312X
Category : Technology & Engineering
Languages : en
Pages : 375
Book Description
Allelopathy is a new field of science, as the term 'Allelopathy' was coined by Prof. Hans Molisch, a German Plant Physiologist in 1937. Till now lot of Allelopathy research work has been done in various fields of Agricultural and Plant Sciences. However, there is no compilation of various Research Methods used. Every scientist is conducting research in his own way. It is causing lot of problems to researchers working in underdeveloped/Third World Countries in small towns without Library facilities. Therefore, to make available the standard methods for conducting allelopathy research independently, this multi-volume book has been planned. Since allelopathy is multi-disciplinary area of research, hence, volumes have been planned for each discipline. Prof. S.S. Narwal has planned this multi-volume Book Research Methods in Plant Sciences: Allelopahty. Three volumes (Volume 1. Soil Analysis, Volume 2. Plant Protection and Volume 3. Plant Pathogens) of this Book have been released during the IV. International Allelopathy Conference, 2004 at Hisar(India). Five volumes (Volume 4. Plant Analysis, Volume 5. Physiological Processes, Volume 6. Biochemical Processes, Volume 7. Forestry/Agroforestry Research and Volume 8. Isolation, Identification and Characterization of allelochemicals are under preparation. Volume 1. Soil Analysis is consists of 20 Chapters, describing the methods to analyse various types of soil properties. The Book is devided into three Sections: General, Physio-chemical properties and Soil microbiology. It provides complete information for Soil Analysis in simple and lucid language. The Figures/ illustrations have been given at appropriate places in text. It will prove very useful to undergraduate and post graduate students and teaching Faculty for Class Room and Laboratory experiments as well as for research.
Introductory Plant Nematology
Author: P. Parvatha Reddy
Publisher: Scientific Publishers
ISBN: 9387991687
Category : Technology & Engineering
Languages : en
Pages : 430
Book Description
This book gives a comprehensive account of all aspects of plant nematology and should be of profound help to the students, teachers, researchers and extension workers alike. The syllabus of ARS Net – Nematology has also been fully covered in this book. Hence, persons appearing for ARS Net – Nematology can also refer this book. The book is divided into eight sections. The first section describes the importance of nematodes in agriculture, presents a historical review, nematode as biological models, entomopathogenic nematodes, and lists the professional societies and their publications.Information on the nematological techniques is outlined in section two.The morphology of nematodes is described and presented in clear schematic drawings in section three. The taxonomic classification along with keys for identification of nematodes up to generic level is provided. In section four, the biology, physiology and ecology of nematodes are described.The host-parasite interactions and symptoms on aerial and under-ground infestation by different nematodes are described and depicted in many photographs in section five. In section six, the interrelationships between nematodes and fungi, bacteria and viruses are discussed.Management of nematode diseases by host resistance and by suppression of nematode population through regulatory, physical, cultural, chemical, biological, and integrated methods have been presented in section seven.The last section of the book discusses the most important nematode induced diseases of horticultural, plantation and spices, commercial and field crops and their management. The selected references provide convenient entry to both current and older literature. Very useful information in the form of common names of nematodes and a glossary of nematological terms are provided in Annexures. This book will give students, teachers, researchers and extension workers with an overview of the entire field of Plant Nematology.
Publisher: Scientific Publishers
ISBN: 9387991687
Category : Technology & Engineering
Languages : en
Pages : 430
Book Description
This book gives a comprehensive account of all aspects of plant nematology and should be of profound help to the students, teachers, researchers and extension workers alike. The syllabus of ARS Net – Nematology has also been fully covered in this book. Hence, persons appearing for ARS Net – Nematology can also refer this book. The book is divided into eight sections. The first section describes the importance of nematodes in agriculture, presents a historical review, nematode as biological models, entomopathogenic nematodes, and lists the professional societies and their publications.Information on the nematological techniques is outlined in section two.The morphology of nematodes is described and presented in clear schematic drawings in section three. The taxonomic classification along with keys for identification of nematodes up to generic level is provided. In section four, the biology, physiology and ecology of nematodes are described.The host-parasite interactions and symptoms on aerial and under-ground infestation by different nematodes are described and depicted in many photographs in section five. In section six, the interrelationships between nematodes and fungi, bacteria and viruses are discussed.Management of nematode diseases by host resistance and by suppression of nematode population through regulatory, physical, cultural, chemical, biological, and integrated methods have been presented in section seven.The last section of the book discusses the most important nematode induced diseases of horticultural, plantation and spices, commercial and field crops and their management. The selected references provide convenient entry to both current and older literature. Very useful information in the form of common names of nematodes and a glossary of nematological terms are provided in Annexures. This book will give students, teachers, researchers and extension workers with an overview of the entire field of Plant Nematology.
Diseases of Horticultural Crops: Nematode Problems and their Management
Author: P. Parvatha Reddy
Publisher: Scientific Publishers
ISBN: 9387307514
Category : Technology & Engineering
Languages : en
Pages : 395
Book Description
Nematodes continue to threaten horticultural crops throughout the world, particularly in tropical and sub-tropical regions. Estimated overall average annual yield loss of the world's major horticultural crops due to damage by plant parasitic nematodes is 13.54%. Monetary losses due to nematodes on 10 horticultural crops, six of which are life sustaining were estimated at US$ 19.37 billion annually based on 1984 production figures and prices. These deleterious effects on plant growth result in reduced yields and poor quality of horticultural crops. Nematode management is therefore, important for high yields and quality that are required by the high cost of modern crop production. The information on nematode diseases and their management, especially crop wise, is very much scattered and there is no book which deals entirely with the above aspects on horticultural crops. This book deals with nematode diseases and their management in horticultural crops such as fruit, vegetable, orname-ntal, medicinal, aromatic, plantation, spice and tuber crops. Each nematode disease is described in adequate detail under the following heads: economic importance, crop losses, distribution, symptoms, hosts range, life cycle, races/ biotypes, host-parasite relationship, histopathology, ecology, spread, survival, interaction with other pathogens and management. The management methods presented includes regulatory, physical cultural, chemical, biological, host resistance and integrated approach. An entire chapter is devoted for sources of availability of critical inputs used for nematode management which would be very useful to the farmers. Very useful information on certain aspects of nematode management is presented in Appendix. The book is adequately illustrated with about 50 figures. This book is a practical guide to practicing farmers of horticultural crops. Further, it is a useful reference to policy makers, research and extension workers and students. The material can also be used for teaching under-graduate and post-graduate courses.
Publisher: Scientific Publishers
ISBN: 9387307514
Category : Technology & Engineering
Languages : en
Pages : 395
Book Description
Nematodes continue to threaten horticultural crops throughout the world, particularly in tropical and sub-tropical regions. Estimated overall average annual yield loss of the world's major horticultural crops due to damage by plant parasitic nematodes is 13.54%. Monetary losses due to nematodes on 10 horticultural crops, six of which are life sustaining were estimated at US$ 19.37 billion annually based on 1984 production figures and prices. These deleterious effects on plant growth result in reduced yields and poor quality of horticultural crops. Nematode management is therefore, important for high yields and quality that are required by the high cost of modern crop production. The information on nematode diseases and their management, especially crop wise, is very much scattered and there is no book which deals entirely with the above aspects on horticultural crops. This book deals with nematode diseases and their management in horticultural crops such as fruit, vegetable, orname-ntal, medicinal, aromatic, plantation, spice and tuber crops. Each nematode disease is described in adequate detail under the following heads: economic importance, crop losses, distribution, symptoms, hosts range, life cycle, races/ biotypes, host-parasite relationship, histopathology, ecology, spread, survival, interaction with other pathogens and management. The management methods presented includes regulatory, physical cultural, chemical, biological, host resistance and integrated approach. An entire chapter is devoted for sources of availability of critical inputs used for nematode management which would be very useful to the farmers. Very useful information on certain aspects of nematode management is presented in Appendix. The book is adequately illustrated with about 50 figures. This book is a practical guide to practicing farmers of horticultural crops. Further, it is a useful reference to policy makers, research and extension workers and students. The material can also be used for teaching under-graduate and post-graduate courses.
Bacteria in Agrobiology: Crop Ecosystems
Author: Dinesh K. Maheshwari
Publisher: Springer Science & Business Media
ISBN: 3642183573
Category : Science
Languages : en
Pages : 438
Book Description
The future of agriculture strongly depends on our ability to enhance productivity without sacrificing long-term production potential. An ecologically and economically sustainable strategy is the application of microorganisms, such as the diverse bacterial species of plant growth promoting bacteria (PGPB). The use of these bio-resources for the enhancement of crop productivity is gaining worldwide importance. Bacteria in Agrobiology: Crop Ecosystems describes the beneficial role of plant growth promoting bacteria with special emphasis on oil yielding crops, cereals, fruits and vegetables. Chapters present studies on various aspects of bacteria-plant interactions, soil-borne and seed-borne diseases associated with food crops such as rice, sesame, peanuts, and horticultural crops. Further reviews describe technologies to produce inoculants, the biocontrol of post harvest pathogens as a suitable alternative to agrochemicals, and the restoration of degraded soils.
Publisher: Springer Science & Business Media
ISBN: 3642183573
Category : Science
Languages : en
Pages : 438
Book Description
The future of agriculture strongly depends on our ability to enhance productivity without sacrificing long-term production potential. An ecologically and economically sustainable strategy is the application of microorganisms, such as the diverse bacterial species of plant growth promoting bacteria (PGPB). The use of these bio-resources for the enhancement of crop productivity is gaining worldwide importance. Bacteria in Agrobiology: Crop Ecosystems describes the beneficial role of plant growth promoting bacteria with special emphasis on oil yielding crops, cereals, fruits and vegetables. Chapters present studies on various aspects of bacteria-plant interactions, soil-borne and seed-borne diseases associated with food crops such as rice, sesame, peanuts, and horticultural crops. Further reviews describe technologies to produce inoculants, the biocontrol of post harvest pathogens as a suitable alternative to agrochemicals, and the restoration of degraded soils.
Integrated Nematode Management in Horticultural Crops
Author: P. Parvatha Reddy
Publisher: Scientific Publishers
ISBN: 9387741125
Category : Technology & Engineering
Languages : en
Pages : 316
Book Description
Nematodes continue to threaten horticultural crops throughout the world, particularly in tropical and sub-tropical regions. Estimated overall average annual yield loss of the world’s major horticultural crops due to damage by plant parasitic nematodes is 13.54%. Monetary losses due to nematodes on 10 horticultural crops, six of which are life sustaining were estimated at US $ 19.37 billion annually based on 1984 production figures and prices. The farmer in his anxiety to contain the nematode pest may resort to indiscriminate use of nematicides posing hazard to the environment. Since the horticultural produce especially fruits and vegetables are consumed afresh, consumers expect residue-free produce both for internal and export markets. In this context, developing ‘Integrated Nematode Management (INM)’ strategy is the challenge before the nematologists. The present book is an attempt which comprehensively deals with both principles and practices of INM. The first part deals with the principles of INM covering aspects such as introduction, role of nematodes in horticulture, interactions with other micro-organisms and nematode management options such as regulatory, physical, cultural, chemical, biological and integrated methods including host resistance. The second part deals with practices for nematode management in horticultural crops such as fruit, vegetable, ornamental, medicinal, aromatic, plantation, spice and tuber crops. This book is a practical guide to practicing farmers of horticultural crops. Further, it is a useful reference to policy makers, research and extension workers and students. The material can also be used for teaching undergraduate and post-graduate courses.
Publisher: Scientific Publishers
ISBN: 9387741125
Category : Technology & Engineering
Languages : en
Pages : 316
Book Description
Nematodes continue to threaten horticultural crops throughout the world, particularly in tropical and sub-tropical regions. Estimated overall average annual yield loss of the world’s major horticultural crops due to damage by plant parasitic nematodes is 13.54%. Monetary losses due to nematodes on 10 horticultural crops, six of which are life sustaining were estimated at US $ 19.37 billion annually based on 1984 production figures and prices. The farmer in his anxiety to contain the nematode pest may resort to indiscriminate use of nematicides posing hazard to the environment. Since the horticultural produce especially fruits and vegetables are consumed afresh, consumers expect residue-free produce both for internal and export markets. In this context, developing ‘Integrated Nematode Management (INM)’ strategy is the challenge before the nematologists. The present book is an attempt which comprehensively deals with both principles and practices of INM. The first part deals with the principles of INM covering aspects such as introduction, role of nematodes in horticulture, interactions with other micro-organisms and nematode management options such as regulatory, physical, cultural, chemical, biological and integrated methods including host resistance. The second part deals with practices for nematode management in horticultural crops such as fruit, vegetable, ornamental, medicinal, aromatic, plantation, spice and tuber crops. This book is a practical guide to practicing farmers of horticultural crops. Further, it is a useful reference to policy makers, research and extension workers and students. The material can also be used for teaching undergraduate and post-graduate courses.
Nematode Management in Plants
Author: P.C. Trivedi
Publisher: Scientific Publishers
ISBN: 9387741702
Category : Technology & Engineering
Languages : en
Pages : 346
Book Description
Nematodes represent a unique challenge to agricultural research, in that they combine the potential for serious reductions in growth and yield in a wide range of crop plants, often with rather nonspecific and easily misdiagnosed symptoms. Development of the concept of pest management and their implementation have led to a greater appreciation of the need for a wide range of tactics for nematode control. The present book ``Nematode Management in Plants'' provides an authoritative review of many aspects of nematode control and progress in the field of nematode management programme. The volume contains eighteen articles covering application of cropping sequences, plant products and botanicals, latex, bioagents and biological control practices for the management of nematode pests. Topics covering use of Azotobacter, Bacillus thuringiensis and VAM Fungi for reducing nematode pests have been specially included to project their role in the present century. Information on Integrated Nematode Management have been included with special emphasis on biocontrol management practices. This book will be useful to Plant Pathologist, Nematologist, research and extension workers, teachers and students.
Publisher: Scientific Publishers
ISBN: 9387741702
Category : Technology & Engineering
Languages : en
Pages : 346
Book Description
Nematodes represent a unique challenge to agricultural research, in that they combine the potential for serious reductions in growth and yield in a wide range of crop plants, often with rather nonspecific and easily misdiagnosed symptoms. Development of the concept of pest management and their implementation have led to a greater appreciation of the need for a wide range of tactics for nematode control. The present book ``Nematode Management in Plants'' provides an authoritative review of many aspects of nematode control and progress in the field of nematode management programme. The volume contains eighteen articles covering application of cropping sequences, plant products and botanicals, latex, bioagents and biological control practices for the management of nematode pests. Topics covering use of Azotobacter, Bacillus thuringiensis and VAM Fungi for reducing nematode pests have been specially included to project their role in the present century. Information on Integrated Nematode Management have been included with special emphasis on biocontrol management practices. This book will be useful to Plant Pathologist, Nematologist, research and extension workers, teachers and students.
Advances in Nematology
Author: P.C. Trivedi
Publisher: Scientific Publishers
ISBN: 9387741680
Category : Technology & Engineering
Languages : en
Pages : 329
Book Description
Plant parasitic nematodes are one of the least understood agricultural pest problems throughout the world. Science of Plant Nematology has grown rapidly is the last three decades. There is a wide gap between the vast information generated for nematode control and that, which is actually utilised. The present book ``Advances in Nematology'' provides an authoritative review account of many aspects of current interest and progress in the field of Plant Nematology that has been made in the recent past. This book includes 21 articles by eminent nematologist on different aspects of the subject. Information on application of molecular biology in nematology, nematodes as biological model, race status in plant parasitic nematodes and nematode vectors of plant diseases have been reviewed covering all major aspects. Nematode diseases on wheat, rice, tobacco, mint, barley and horticultural crops and their management, specially in context to Indian scenario have been covered. Newer approaches for the management of plant parasitic nematodes including use of VAM fungi, biocontrol agents and integrated nematode management strategies have been included to project out their use on field scale. Articles on role of nematodes in disease complexes with fungi, genetic studies on the resistance of barley, breeding for nematode resistance in forage legumes and nematode pests of economically important crops in India and their managements have been added to the value of the book. Scholars and students of Nematology, researchers and extension workers and plant pathologist will find this book very useful.
Publisher: Scientific Publishers
ISBN: 9387741680
Category : Technology & Engineering
Languages : en
Pages : 329
Book Description
Plant parasitic nematodes are one of the least understood agricultural pest problems throughout the world. Science of Plant Nematology has grown rapidly is the last three decades. There is a wide gap between the vast information generated for nematode control and that, which is actually utilised. The present book ``Advances in Nematology'' provides an authoritative review account of many aspects of current interest and progress in the field of Plant Nematology that has been made in the recent past. This book includes 21 articles by eminent nematologist on different aspects of the subject. Information on application of molecular biology in nematology, nematodes as biological model, race status in plant parasitic nematodes and nematode vectors of plant diseases have been reviewed covering all major aspects. Nematode diseases on wheat, rice, tobacco, mint, barley and horticultural crops and their management, specially in context to Indian scenario have been covered. Newer approaches for the management of plant parasitic nematodes including use of VAM fungi, biocontrol agents and integrated nematode management strategies have been included to project out their use on field scale. Articles on role of nematodes in disease complexes with fungi, genetic studies on the resistance of barley, breeding for nematode resistance in forage legumes and nematode pests of economically important crops in India and their managements have been added to the value of the book. Scholars and students of Nematology, researchers and extension workers and plant pathologist will find this book very useful.