The author wishes to express his gratitude to the MEKARN project, supported by SIDA/SAREC of Sweden for financing this study; to Dr. T.R Preston, Director of the University of Tropical Agriculture (UTA), for advice and allowing the use of the library of UTA both electronic and hard documents.
My thanks to Ass. Professor Dr. Brian Ogle, International coordinator, Dr Luu Trong Hieu, regional coordinator of SIDA/SAREC, who have organized this course.
My great thanks to all my teachers who gave the useful lectures and encouraged me during the courses; and to my classmates, from Laos, Thailand and Vietnam who have helped me and gave warm hospitality during the study.
Last but not least, I my grateful to my wife Hout Chantha and my son Kouch Sothakongs for their love and encouragement.