00660nam a2200205Ia 4500 CTU_30158 210402s9999 xx 000 0 und d 631 Z27 H G Zandstra A methodology for on-farm cropping systems research H G Zandstra, E C Price, J A Litsinger, R A Morris IRRI Philippines IRRI 1981 Hệ thống canh tác,Hệ thống canh tác XH893,NN605 agriculture - research - on-farm,cropping systems Liên, 990312 Trung tâm Học liệu Trường Đại học Cần Thơ