2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/158605We obtain a detailed classification for a class of non-simply connected Calabi-Yau threefolds which are of potential interest for a wide range of problems in string phenomenology. These threefolds arise as quotients of Schoen's Calabi-Yau threefolds, which are fiber products over P1 of two rational elliptic surfaces. The quotient is by a freely acting finite abelian group preserving the fibrations. Our work involves a classification of restricted finite automorphism groups of rational elliptic surfaces.50 pages; v3: version published in CNTPAlgebraic GeometryHigh Energy Physics - Theory14J50 (Primary), 14D06, 14J27, 14J32 (Secondary)text