In addition, Pondo, Gonge, Tale, Laka, Pam and To are unclassified within Mbum. To is a secret male initiation language of the Gbaya. Dek is purported in some sources but apparently unattested.
La'bi, an esoteric ritual language of male initiation among the Gbaya Kara, the Mbum, and some Sara Laka, is related to Mbum. It has substantial loans from one or more Sara languages.[2] Other initiation languages in the Mbum family are To (Gbaya, but with partial Mbum origins), Dzel, and Ngarage.[3]
^Boyd, Raymond. 1974. Étude Comparative dans le groupe Adamawa. (Société d'études linguistiques et anthropologiques de France, 46.) Paris: Centre National de la Récherche Sciéntifique
^Yves Moñino, 1977. "Conceptions du monde et langue d'initiation la'bi de Gbaya-Kara", Langages et cultures africaines, Paris, Maspero.
^Elders, Stefan. 2006. Issues in comparative Kebi-Benue (Adamawa). Africana Linguistica XII. 37-88.