Trimberger GW : Breeding efficiency in dairy cattle from artificial insemination at various intervals before and after ovulation, Nebraska Agri Exp Stn Res Bull, 153, 3-25(1948)
Trimberger GW, Davis HP : Conception rate in dairy cattle from artificial insemination at various stages of estrus, Nebraska Agri Exp Stn Res Bull, 129, 1-14 (1943)