Sugar, A. (2017). Uyghur-ip as a verb linker in multiple constructions. Proceedings of the Linguistic Society of America, 2, 16-1. Link
Uyghur grammars and linguistic works have traditionally described the -ip morpheme as a suffix that derives adverbs from verbs (Tomur 2003, Tohti 2012). This paper uses structural diagnostics involving passive morphology, single negation and NPI licensing to argue that -ip is a functional head with multiple syntactically distinct roles in different structures. The distinct properties of these structures, according to the types of verbs that are linked by -ip, provide evidence against a uniform derivational process of adverb formation. In some case -ip allows for adjunction of a TP-sized constituent, suggesting it may be a non-finite T head. In other cases it allows for adjunction of a verb phrase, and in yet another case it creates a lexical verb + auxiliary sequence in a monoclausal structure. I suggest that -ip in the latter two cases may be an event head.
A paper on Uyghur linguistics that I’m not going to pretend to understand.