共 7 条
[1]
HAYS H, 1975, ANNUAL CROP RAW DATA
[2]
HEADY EO, 1952, ECONOMICS AGRICULTUR
[3]
HEADY EO, 1952, J FARM ECONOMICS, V34, P2
[4]
NORMAN DW, 1972, 37 A BELL U I AGR RE
[5]
NORMAN DW, 1974, J DEV STUDIES, V11, P1
[6]
NORMAN DW, 1972, 19 A BELL U I AGR RE
[7]
OGUNFOWORA O, 1972, THESIS IOWA STATE U