2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/79141Nondegenerate plane congruences in the four-dimensional complex projective space with degenerate general focal conic are classified by using the focal method due to Corrado Segre.Latex, 14 pagesAlgebraic Geometry14N05 (Primary); 51N35 (Secondary)text