The structure of this subject agreement paradigm can be traced back to Proto-Sepik, although the morphemes themselves do not seem to be directly related to the reconstructed Proto-Sepik forms. (See also Sepik languages#Gender.)
^ abcdFoley, William A. (2018). "The Languages of the Sepik-Ramu Basin and Environs". In Palmer, Bill (ed.). The Languages and Linguistics of the New Guinea Area: A Comprehensive Guide. The World of Linguistics. Vol. 4. Berlin: De Gruyter Mouton. pp. 197–432. ISBN978-3-11-028642-7.