In this paper, we investigate the notions of-projective,-injective, and-flat modules and give
some characterizations of these modules, where is a class of left modules. We prove that the …

Let be a ring, a class of left-modules, the class of submodules of, and the class of quotient-
modules of. It is shown that is precovering (preenveloping) if and only if every injective …

RINGS OVER WHICH FLAT COVERS OF SIMPLE MODULES ARE PROJECTIVE Page 1
Journal of Algebra and Its Applications Vol. 11, No. 3 (2012) 1250046 (7 pages) c© World …

Throughout this paper, T is a ring with identity and F is a unitary left module over T. This
paper study the relation between semihollow-lifting modules and semiprojective covers …

In Bican et al., it is proved that all modules over an arbitrary ring have flat covers. In this
article, we shall study rings over which flat covers of finitely generated modules are …

Let M be a module. A\delta-cover of M is an epimorphism from a module F onto M with
a\delta-small kernel. A\delta-cover is said to be a flat\delta-cover in case F is a flat module. In …

We prove the following results for a ring R.(a) If C is a class of right R-modules closed under
direct summands and isomorphisms, then every right R-module has an epic C-envelope if …

Let $ R $ be a ring and $ M $ be an $ R $-module. In this paper we investigate modules $ M
$ such that every (simple) cosingular $ R $-module is $ M $-projective. We prove that every …

We show that a ring R is right perfect if and only if every right R-module has a semi-
projective cover. We characterize (semi) hereditary and semisimple rings via semiprojective …