Whitfield, Alan K, Kok, H M. J.L.B. Smith Institute of Ichthyology, Rhodes University, Grahamstown, South Africa; . Recruitment of juvenile marine fishes into permanently open and seasonally open estuarine systems on the southern coast of South Africa.

Whitfield, Alan K, Paterson, Angus W, Bok, Anton H, Kok, H M. A comparison of the ichthyofaunas in two permanently open eastern Cape estuaries. 1994.