The notation and terminology used in this paper have been introduced in the following articles: [20], [9], [25], [7], [8], [4], [16], [24], [21], [19], [13], [18], [23], [1], [2], [10], [5], [17], [11], [3], [22], [14], [12], [6], [26], and [15]. We use the following convention: i, j, n denote natural numbers, f , g, h, k denote finite sequences of elements of R, and M , N denote non empty metr...