De Kock, K., and C. Wolmarans. “Distribution and Habitats of Gyraulus Costulatus, Potential Snail Intermediate Host of Intestinal Flukes of the Family Echinostomatidae in South Africa”. Suid-Afrikaans Tydskrif Vir Natuurwetenskap En Tegnologie / <i>South African Journal of Science and Technology</I&gt;, Vol. 25, no. 1, Sept. 2006, pp. 19-31, doi:10.4102/satnt.v25i1.141.