“…A large number of works are noted in [1,2,3,8,11,12,15,17,18,20] and the relevant literature therein. Unfortunately, recently these problems became not attractive since some scholars found the equivalence of fixed point results between cone metric spaces and metric spaces, also between cone b-metric spaces and b-metric spaces (see [4,5,6,7,13,14]). However, quite fortunately, very recently, Liu and Xu [16] introduced the notion of cone metric space over Banach algebra and considered fixed point theorems in such spaces in a different way by restricting the contractive constants to be vectors and the relevant multiplications to be vector ones instead of usual real constants and scalar multiplications.…”