From the introduction: "A lexicostatistic survey was conducted in early 1985 as part of a comprehensive study of the languages spoken in the Zambales Mountains of the Philippines. The survey involved the collection and analysis of some forty word lists, resulting in the definition of six distinct languages in an area whose linguistic situation had previously been relatively unknown. This paper presents these survey findings in the form of a language tree, and introduces a general-use computer program which greatly enhanced the accuracy and speed of the lexicostatistic analysis."
Wimbish, John S.
"The languages of the Zambales mountains: A Philippine lexicostatistic study,"
Work Papers of the Summer Institute of Linguistics, University of North Dakota Session: Vol. 30, Article 8.
Available at: https://commons.und.edu/sil-work-papers/vol30/iss1/8