查看文章

Let R be a ring and n, k two non-negative integers. In this paper, we introduce the concepts of n-weak injective and n-weak flat modules and via the notion of special super finitely presented modules, we obtain some characterizations of these modules. We also investigate two classes of modules with richer contents, namely and which are larger than that of modules with weak injective and weak flat dimensions at most k. Then over any arbitrary ring, we study the existence of and covers and pre-envelopes.