2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/148763This paper presents the construction of the Seiberg-Witten-Floer homology of three-manifolds with non-trivial rational homology, and some properties of the invariant of three-manifolds obtained by computing the Euler characteristic. This new version corrects a mistake and some misprints that appear in the published version (Internat. J. Math., Vol.7, N.5 (1996) 671-696). Various sections are rewritten in more detail.46 Pages, LaTex, no figuresDifferential Geometry57R57, 55N35, 58E05text