... Banach contraction principle in complete cone metric spaces,” Fixed Point Theory and Applications, vol 2008, Article ID 768294, 11 pages, 2008 P Vetro, “Common fixed points in cone metric spaces,” ... pairs on cone metric spaces,” Fixed Point Theory and Applications, vol 59, Article ID 643840, 13 pages, 2009 15 J O Olaleru and H Akewe, “An extension of Gregus fixed point theorem,” Fixed Point Theory ... subspace of X, then the mappings f and g have a unique common fixed point Moreover, for any xo ∈ X, the sequence {f xn } of the initial point xo , f xn−1 for all n, converges to the fixed point where...