Sobreiro, B. P., A. M. Lucon, F. F. Pasqualotto, J. Hallak, K. S. Athayde, and S. Arap. “Semen Analysis in Fertile Patients Undergoing Vasectomy: Reference Values and Variations According to Age, Length of Sexual Abstinence, Seasonality, Smoking Habits and Caffeine Intake”. São Paulo Medical Journal, vol. 123, no. 4, July 2005, pp. 161-6, https://periodicosapm.emnuvens.com.br/spmj/article/view/2345.