De Heusch, L., Utotombo, l'Art d'Afrique noire dans les collections privées belges, Brussels, 1988; Robbins, W. and Nooter, N., African Art in American Collections, Washington, D.C., 1989; Vogel, S. (ed.), For Spirits and Kings African Art from the Paul and Ruth Tishman Collection, New York, 1981; Felix, M., 100 Peoples of Zaire and their Sculpture, Brussels, 1987; Roy, C., Art of the Upper Volta Rivers, Arcueil, 1987; and twelve others of similar interest (17)