Ferreira, Marcelle Christine Nascimento, et al. “Evaluation of the Pregnancy Rate in Multiparous Nellore Cows under Artificial Insemination and Fixed-Time Artificial Insemination”. Brazilian Journal of Veterinary Medicine, vol. 34, no. 2, June 2012, pp. 152-6, https://bjvm.org.br/BJVM/article/view/694.