In current linguistic theory [Chomsky, Noam, 1991, Some notes on economy of derivation and representation, in Freidin, R., ed., “Principles and parameters in comparative grammar”, MIT Press, Cambridge, MA, pp. 417-454; Ouhalla, J., 1991, “Functional categories and parametric variation”, London, Routledge; Pollock, J.-Y., 1989, Verb-movement, UG, and the structure of IP, “Linguistic Inquiry” 20, pp. 365-424] phrasal structure is projected from those elements that participate in theta-marking relationships and from functional categories. (The former comprise predicates and their arguments; the latter comprise free morphemes such as modals, auxiliares, determiners, complementizers [...]).
- Zobl & Liceras (2004), Pag. 231