Soppitt, C. A. 1885. "A Short Account of the Kachcha Naga (Empeo) Tribe in the North Cachar Hills: with An Outline Grammar, Vocabulary and Illustrative Sentence." Assam Secretariat Press.
Snapp, Allen, John Anderson and Joy Anderson. 1982. "Northern Paiute." In Uto-Aztecan Grammatical Sketches, edited by R. W. Langacker. 3: 1-92. Summer Institute of Linguistics and University of Arlington.
Shoemaker, Jack S. and Nola K. Shoemaker. 1967. "Essejja." In Bolivian Indian grammars 1, edited by Esther Matteson. 16: 209-283. Summer Institute of Linguistics of the University of Oklahoma.