Barlow, Russell Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Max Planck Society;
http://scholarspace.manoa.hawaii.edu/handle/10125/37432 (Any fulltext)
Barlow, R. (2016). Ulwa (East Sepik, Papua New Guinea): Language materials from the Ulwa [yla] language of East Sepik, Papua New Guinea. Honululu: Kaipuleohone, the University of Hawai‘i Digital Ethnographic Archive.