M. Stahl, Sachak, N., y Mkusa, G.,
«Water to the villages : a socio-economic study of water-related problems in Northern Njombe», vol. no. 54. University of Dar es Salaam, Bureau of Resource Assesssment and Land Use Planning, Dar es Salaam, Tanzania, p. 2, 91 p. : fig., tab., 1979.