We prove that (a) if R is a left coherent ring, then the weak global dimension w D (R)<= n
(n>= 2) if and only if every (n–2) th F–cosyzygy of a finitely presented right R–module has a …

If R is left noetherian and M is a left R-module, then we can construct a complex called an
injective resolvent of M using injective precovers. Likewise, if R is left coherent and M is a …

Let R be any ring. A right R-module M is called n-copure projective if Ext1 (M, N)= 0 for any
right R-module N with fd (N)≤ n, and M is said to be strongly copure projective if Ext i (M, F) …

A ring R is called left P-coherent in case each principal left ideal of R is finitely presented. A
left R-module M (resp. right R-module N) is called D-injective (resp. D-flat) if Ext1 (G, M)= 0 …

Flat envelopes in commutative rings Page 1 ISRAEL JOURNAL OF MATHEMATICS, Vol. 62,
No, 1, 1988 FLAT ENVELOPES IN COMMUTATIVE RINGS BY J. ASENSIO MAYOR AND J …

Let R be a ring. A left R-module M (resp., right R-module N) is called weak injective (resp.,
weak flat) if (resp.,) for every super finitely presented left R-module F. By replacing finitely …

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 left coherent ring, S any ring and RωS an (R, S)-bimodule. Suppose ωS has an
ultimately closed FP-injective resolution and RωS satisfies the conditions:(1) ωS is finitely …

Let R be a ring, and n and d fixed non-negative integers. An R-module M is called (n, d)-
injective if Ext d+ 1 R (P, M)= 0 for any n-presented R-module P. M is said to be (n, d) …

868 MARTINEZ HERNANDEZ where F'is a flat and F-divisible module, can be completed
commutatively. b) The diagram can be completed only by means of autornorphisms of F. In …