Using R-dual modules we obtain an exact sequence of ExtnR(M,R) and show that for a coherent left perfect ring R,the finitely presented dimensions of ExtmR(M,R),m≥0 is less than that of M,which generalizes the corresponding result in[1].
利用R-偶模得到了ExtnR(M,R)的正合列,证明了在凝聚左完全环R下,ExtRm(M,R),(m≥0)的有限表示维数不超过M的有限表示维数,推广了文献[1]的结果。