共 29 条
[11]
JEPSEN RL, 1981, MF636 KANS STAT U EX
[12]
MCKNIGHT RH, 1984, 845507 AM SOC AGR EN
[13]
MURPHY DJ, 1985, 319 PENN STAT U EXT
[14]
PIERCY LR, 1984, 845508 AM SOC AGR EN
[15]
PURSCHWITZ MA, 1987, 1987 P NIFS SUMM M C
[16]
PURSCHWITZ MA, 1986, 866 NAT I FARM SAF P
[17]
SCHNIEDER RD, 1986, 865512 AM SOC AGR EN
[18]
SCHRAMM CJ, 1973, SUPPLEMENTAL STUDIES, P137
[19]
SCHULTZ LD, 1985, MINNESOTA FARM WORK
[20]
STEWART LE, 1977, EXTENSION B U MARYLA, V255