1. Casida LE: The postpartum interval and its relation to fertility in the cow, sow and ewe. J. Anim. Sei. (Suppl. 1). 1971, 32, 66–72.
2. Clapp H: A factor in breeding efficiency of dairy cattle. Proc. Amer. Soc. Anim. Prod. 1937, 37, 259–265.
3. Cooper DA, Carver DA, Villeneuve P, Silvia WJ, Inskeep EK: Effects of progestagen treatment on concentrations of prostaglandins and oxytocin in plasma from the posterior vena cava of post-partum beef cows. J. Reprod. Fertil. 1991, 91, 248–262.
4. Copelin JP, Smith MF, Garverick HA, Youngquist RS: Effect of uterus on subnormal luteal function in anoestrus beef cows. J. Anim. Sci. 1987, 64, 1505–1511.
5. Copelin JP, Smith MF, Keisler DH, Garverick HA: Effect of active immunization of pre-partum and post-partum cows against prostaglandin F2a on lifespan and progesterone secretion of shortlived corpora lutea. J. Reprod. Fert. 1989, 87, 199–207