Endangered Languages Catalogue Project. Compiled by research teams at University of Hawai'i Mānoa and Institute for Language Information and Technology (LINGUIST List) at Eastern Michigan University . (2012) ·

Ethnologue: Languages of the World, 16th Edition (2009) . (2009) · edited by M. Paul Lewis · SIL International http://www.ethnologue.com/

Precolonial African Intergroup Relations in the Kauru and Pengana Polities of Central Nigerian Highlands 1800-1900 . J. G. Nengel (1999) · European University Studies: Series III · Vol. 814 · Frankfurt am Main: Peter Lang