F. F. de Souza, D. P. Leme, E. Uechi, L. A. Trinca, and M. D. Lopes, “Evaluation testicular fine needle aspiration cytology and serum testosterone levels in dogs”, Braz. J. Vet. Res. Anim. Sci., vol. 41, no. 2, pp. 98-105, Apr. 2004.