Fas was once mistakenly placed in the Kwomtari family, confusing their classification. Its only demonstrated relative is actually Baibai, with which it is 40% cognate. See Fas languages for details.
Baron, Wietze (1983a). "Cases of counter-feeding in Fas". Language and Linguistics in Melanesia. 14: 138–149. OCLC9188672.
Blake, Fiona (2007). Spatial Reference in Momu (BA thesis). The University of Sydney. hdl:2123/1919.
Honeyman, Thomas Tout (2016). A grammar of Momu, a language of Papua New Guinea (PhD thesis). Australian National University. doi:10.25911/5d70f1b69a565. hdl:1885/132961.