2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/67939We study the set of rational curves of a certain topological type in general members of certain families of Calabi-Yau threefolds. For some families we investigate to what extent it is possible to conclude that this set is finite. For other families we investigate whether this set contains at least one point representing an isolated rational curve.In special volume dedicated to Steven L. Kleiman on his 60'th birthday. Contains revised version of Theorem 4.3Algebraic Geometry14J32 (14H45, 14J28)text