“…A well known, several generalizations of standard metric spaces have appeared. In particular, asymmetric metric spaces were introduced by Wilson [21] and then studied by many authors (see [1,11,13,16]). In 2000, for the first time generalized metric spaces were introduced by Branciari [3], in such a way that triangle inequality is replaced by the quadrilateral inequality d(x, y) ≤ d(x, z) + d(z, u) + d(u, y) for all pairwise distinct points x, y, z and u.…”