Jonathan Derrick, "The 'Germanophone' Elite of Douala under the French Mandate." Journal of African History (1980): 255-267 online.
Stern 1957, pp. 487–506. Stern, Theodore (1957). "Drum and Whistle "Languages": An Analysis of Speech Surrogates". American Anthropologist. 59 (3): 487–506. ISSN0002-7294. JSTOR665914.
Stern 1957, pp. 487–506. Stern, Theodore (1957). "Drum and Whistle "Languages": An Analysis of Speech Surrogates". American Anthropologist. 59 (3): 487–506. ISSN0002-7294. JSTOR665914.