Schumacher, J.

Langan, J.N.; Ramsay, E.C.; Schumacher, J.; Chism, T.; Adair, S. 2001. Diagnosis and management of a patent urachus in a white rhinoceros calf (Ceratotherium simum simum). Journal of Zoo and Wildlife Medicine 32 (1): 118-122, figs. 1-2.

Radcliffe, R.W.; Schumacher, J.; Hartsfield, S.M.; Merritt, A.M.; Murray, M.J. 1998. Idiopathic distal esophageal dilation in a southern black rhinoceros (Diceros bicornis minor). Journal of Zoo and Wildlife Medicine 29 (4): 465-469, figs. 1-3.