Lewis, M. Paul, ed. (2009). "Ngombe". Ethnologue: Languages of the World, Sixteenth edition (online). Dallas, Tex.: SIL International. Archived from the original on Dec 19, 2011. Retrieved September 3, 2010.
Lewis, M. Paul, ed. (2009). "Ngombe". Ethnologue: Languages of the World, Sixteenth edition (online). Dallas, Tex.: SIL International. Archived from the original on Dec 19, 2011. Retrieved September 3, 2010.