Headland, Thomas N. and Janet D. Headland. 1974. "A Dumagat (Casiguran) - English Dictionary." 28: Canberra: Research School of Pacific and Asian Studies, Australian National University.
Headland, Thomas N. 2003. "Thirty Endangered Languages in the Philippines." In Work Papers of the Summer Institute of Linguistics, University of North Dakota Session, 47:
Headland, Thomas N. Why Foragers Do Not Become Farmers: A Historical Study of a Changing Ecosystem and Its Effect On a Negrito Hunter-gatherer Group in the Philippines. PhD thesis, University of Hawaii, 1986.
Haan, Johnson Welem. The Grammar of Adang: A Papuan Language Spoken On the Island of Alor East Nusa Tenggara - Indonesia. PhD thesis, University of Sydney, 2001.
Guy, J. B. M. 1974. "A Grammar of the Nortern Dialect of Sakao." 33: Canberra: Research School of Pacific and Asian Studies, Australian National University.
Grimes, Charles E. 2009. "Digging For the Roots of Language Death in Eastern Indonesia: The Cases of Kayeli and Hukumina." In Endangered Languages of Austronesia, edited by Margaret Florey. 73-89. Oxford University Press.