His research varies from phrase structure theory to Irish Phonology, but much of his work has centered on the analysis of VSO languages in general and Celtic in particular. In addition to writing numerous research articles, he is the co-editor of two volumes on the syntax of VSO languages (Carnie & Guilfoyle 2000, Carnie, Harley & Dooley 2005), and is the author of Blackwell's textbook _Syntax: A Generative Introduction._ Versions: