“…The theoretical studies are advancing in two main directions: one of them is related with the attempts to generalize the contractive conditions on the maps and thus, weaken them; the other with the attempts to generalize the space on which these contractions are defined. Among the results in the first direction one can mention cyclic contractions, almost contractions, non-expansive and expansive maps [3,4,28,29,30,31,32,33,34,37,50]. In the second direction some of the most extensively studied fields are the cone metric spaces, partial metric spaces and G-metric spaces [1,2,6,7,8,9,10,12,15,16,17,20,21,39,40].…”