Andreeva, Madlena, et al. “EVALUATION OF THE CRYOTOLERANCE OF SPERMATOZOA IN SOFIA (ELIN-PELIN) SHEEP BREED”. TRADITION AND MODERNITY IN VETERINARY MEDICINE, vol. 8, no. 1, June 2023, pp. 11-16, https://scij-tmvm.com/index.php/pub/article/view/226.