Literature
- Buskirk, J. R. 1989b. Field observations on Phrynops williamsi and other Uruguayan chelonians. Vivarium 1(4): 8-11.
- Rhodin, A. G. J., and R. A. Mittermeier. 1983. Description of Phrynops williamsi, a new species of chelid turtle of the South American P. geoffroanus complex. In: A. G. J. Rhodin and K. Miyata (eds.), Advances in Herpetology and Evolutionary Biology, pp. 58-73. Mus. Comp. Zool. Harvard. Cambridge, Mass.