Found:

coreference

SYNTAX: if two referential elements (NPs) in a structure refer to the same entity, i.e. have the same reference, this is called coreference. EXAMPLE: in John says that he has been here before, the NPs John and he can be co-referential. Coreference is usually indicated by coindexing: John_i says that he_i has been here before.

LIT.	Chomsky, N. (1981) Fiengo, R. and R. May (1994) Lasnik, H. (1989)