Mussabekov Aidos, Shamshidin Aljan, and Alshinbaev Orynbasar. “Influence of Age on Sperm production’s Indicators of Bulls”. Scientific Journal of Animal Science, vol. 5, no. 8, Aug. 2016, pp. 339-41, https://www.sjournals.com/index.php/sjas/article/view/182.