List of sources:
De Bruyn, G.F.C. Professore: Universiteit van Stellenbosch en voorgangers. Kaapstad: Nasionale Handelsdrukkery, 1989.
De Villiers, O.T. The blood of the ostrich. Onderstepoort Journal of Veterinary Science and Animal Industry, 1938, Vol. 11, pp. 419-504.
FamilySearch: Ockert Tobias de Villiers. https://www.familysearch.org/ark:/61903/3:1:33S7-LBHQ-95D?view=index&personArk=/ark:/61903/1:1:Q2Y8-K73Q&action=view and https://www.familysearch.org/tree/person/details/G814-B3P
Google scholar. http://scholar.google.co.za Publications by O.T. de Villiers.
Posthumus, P.J. Past Veterinarians in South Africa, Vol. 1, 10th edition, [1992].