Research in Tanzania, 1971: Pangani River, Eastern and Western Usambaras, Mt. Meru (Determinants of group size in East African Black-and-White Colobus); and Kenya, 1972: Tana River (Survey and census of Tana River Red Colobus and Mangabey)

1973 Notes on the Ecology and Behaviour of the Angola Colobus (Colobus angolensis) in N.E. Tanzania. Folia Primat. 20:12-26.

Angola colobus (Colobus angolensis palliatus) in gallery forest on Pangani River, Tanzania

1974 (with P. Andrews and J.F.M. Horne). The Tana Colobus and Mangabey. Oryx 12:565-575.

1975 (with P. Andrews and J.F.M. Horne). Ecology of the Tana River Floodplain, Kenya. J. E. Afr. N.H. Soc. Nat. Mus. 151:1-31.

1976 River of Monkeys. Hemisphere, 20(9):28-32.

1978 Phylogenetic and population systematics of the Mangabeys (Primates: Cercopithecoidea). Primates 19:1-34.

1981 Survey of the Tana river Colobus and Mangabey. National Geographic Society Research Reports 13:235-242.

Tana River Mangabey (Cercocebus galeritus) at Mnazini, Tana River, Kenya

Tana River Red Colobus (Piliocolobus rufomitratus) at Hewani, Tana River, Kenya