共 7 条
- [1] BOYD GB, 1971, SW23C US ENV PROT AG
- [3] DAVIDSON GR, 1972, SW83TS US ENV PROT A
- [4] Richardson RA, 1974, SO J AGR EC, V06, P143, DOI [10.1017/S0081305200012012, DOI 10.1017/S0081305200012012]
- [5] RICHARDSON RA, 1975, 920 PURD U AGR EXP S
- [6] Spillers P. D., 1973, Southern Journal of Agricultural Economics, V5, P185
- [7] WERTH J, 1976, LANCET, V2, P263