  In this paper, we firstly prove the existence of the equilibrium for the
generalized abstract economy. We apply these results to show the existence of
solutions for systems of vector quasi-equilibrium problems with multivalued
trifunctions. Secondly, we consider the generalized strong vector
quasi-equilibrium problems and study the existence of their solutions in the
case when the correspondences are weakly naturally quasi-concave or weakly
biconvex and also in the case of weak-continuity assumptions. In all
situations, fixed-point theorems are used.
