2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/68096We introduce the notion of b-sequence for finitely generated modules over Noetherian rings, which characterizes long Bourbaki sequences. Our main concern is an application of this notion to generalized Cohen-Macaulay approximation, which we introduced lately. We will show how we can construct long Bourbaki sequences of non-trivial type characterizing generalized Cohen-Macaualy ideals by finding suitable b-sequences.This is a largely enhanced version of "Single spot ideals of codimension 3 and long Bourbaki sequences"(math.AC/0303384)Commutative Algebra13C99, 13D45text