Morais, R. N. de, R. G. Mucciolo, and W. G. Viana. “Reproductive Biology of Donkey. II. Physycal and Morfhologycal Characteristics of Semen”. Brazilian Journal of Veterinary Research and Animal Science, vol. 31, no. 1, Mar. 1994, pp. 49-57, doi:10.11606/issn.1678-4456.bjvras.1994.52049.