Brunckhorst, Claudia Stoll, et al. “Elective Interruption of Pregnancy in Dogs (Canis Familiaris, Linnaeus, 1758)”. Brazilian Journal of Veterinary Research and Animal Science, vol. 37, no. 3, Jan. 2000, pp. 221-8, https://doi.org/10.1590/S1413-95962000000300009.