Garcês, A., I. Pires, N. Alvura, A. Gama, A. Alves, F. Silva, and P. Rodrigues. “Volvulus in a 20 Years Old Captive Hippopotamus (Hippopotamus Amphibius, Linnaeus, 1758)”. Journal of Advanced Veterinary Research, vol. 10, no. 4, Oct. 2020, pp. 261-2, https://www.advetresearch.com/index.php/AVR/article/view/529.