共 99 条
[12]
COOK RL, 1962, SOIL MANAGEMENT CONS
[13]
DARMSTADTER J, 1971, ENERGY WORLD ECONOMY
[15]
DEGRAFF HF, 1943, AGR ECON
[16]
DELROIT RJ, 1953, CROP PRODUCTION
[17]
DREW J. S., 1966, Illinois Agricultural Economics, V6, P25, DOI 10.2307/1348785
[18]
DYAL RS, 1963, NATIONAL S POULTRY I
[19]
EPP AW, 1954, 426 NEBR EXP STA B
[20]
EVERETT HL, PERSONAL COMMUNICATI