Historically, Kurtöp and its speakers have had close contact with speakers of Bumthang, Nupbi and Kheng languages, nearby languages of central and eastern Bhutan to the extent that they may be considered part of a wider collection of "Bumthang languages".
Hyslop, G. (2008a). Morey, S., Post, M., ed. "Kurtöp phonology in the context of Northeast India". North East Indian Linguistics 1: Papers from the First International Conference of the North East Indian Linguistic Society (Cambridge: Cambridge University Press): 3–25.
Hyslop, G. (2008b). "Kurtöp and the classification of the languages of Bhutan". South Asian Linguistics, Case, Voice, and Language Coexistence. Proceedings from the 42nd Annual Meeting of the Chicago Linguistic Society 42 2. Chicago: University of Chicago Press.
Hyslop, G. (2009). "Kurtöp Tone: A tonogenetic case study". Lingua 119. pp. 827–845.