Africa ( ch. 7 ) . Gerrit J. Dimmendaal and F. K. Erhard Voeltz (2007) · In Encyclopedia of the World's Endangered Languages edited by Christopher Moseley · Routledge

Personal Communication on Ts'exa Language . Matthias Brenzinger and Anne-Maria Fehn (2012) ·

Patterns of Linguistic Convergence in the Khoe-speaking Area of Southern Africa ( pp. 189-200 ) . Rainer Vossen (2011) · In Geographical Typology and Linguistic Areas: With Special Reference to Africa edited by Osamu Hieda and Christa König and Hirosi Nakagawa · John Benjamins Publishing Company

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) ·