2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/120737A collection C of subgroups of a finite group G can give rise to three different standard formulas for the cohomology of G in terms of either: the subgroups in C; or their centralizers; or their normalizers. We give a short but systematic study of the relationship among such formulas for nine standard collections C of p-subgroups, obtaining some new formulas in the process. To do this, we exhibit some sufficient conditions on the poset C which imply comparison results.12 pages. Extra counterexamples added. To appear in Advances in MathAlgebraic TopologyGroup Theory20J06 (Primary); 20J05, 55R35, 55P91 (Secondary)text