Aritonang, Tetty Rina, et al. “The Role of FSH, LH, Estradiol and Progesterone Hormone on Estrus Cycle of Female Rats”. International Journal of Sciences: Basic and Applied Research (IJSBAR), vol. 35, no. 1, July 2017, pp. 92-100, https://www.gssrr.org/JournalOfBasicAndApplied/article/view/7834.