Found:

COMP

SYNTAX: the category of the complementizer of embedded clauses. In languages exhibiting the Verb Second phenomenon the COMP position is the ultimate landing site of the finite verb in root clauses. Originally it was assumed that wh-phrases such as who in who did you see?, is in the COMP-position in order to explain why, in English, the presence of a wh-phrase usually excludes the presence of a complementizer (Doubly-Filled COMP filter). The standard assumption now is that COMP, or rather C⁰, heads its own syntactic projection - CP - and that wh-phrases, relative pronouns and other preposed material are in the specifier position of CP.

LIT.	Chomsky, N. (1986b) Lasnik, H. and M. Saito (1992) Riemsdijk, H. van and E. Williams (1986)