“…The past decade has seen a new semigroup-theoretical approach. This approach was first introduced by Facchini and Wiegand [29] and has been used by several authors (for example, see [3], [4], [7], [8], [19], [22], [25], [26], [27], [28], [29], [46], [49], and [57]). Let R be a ring and let C be a class of right R-modules which is closed under finite direct sums, direct summands, and isomorphisms.…”