  In this paper we deal with two classes of mixed metric 3-structures, namely
the mixed 3-Sasakian structures and the mixed metric 3-contact structures.
Firstly we study some properties of the curvature of mixed 3-Sasakian
structures, proving that any manifold endowed with such a structure is
Einstein. Then we prove the identity between the class of mixed 3-Sasakian
structures and the class of mixed metric 3-contact structures.
