2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/64464The existence of closed hypersurfaces of prescribed curvature in semi-riemannian manifolds is proved provided there are barriers.25 pages, amslatex, A pdf version can be retrieved from http://www.math.uni-heidelberg.de/studinfo/gerhardt/preprints and bibtex data from http://www.math.uni-heidelberg.de/studinfo/gerhardt/bibtexcg01b.html v2 Table of Contents added, smaller pointsize chosenDifferential Geometry35J60, 53C21, 53C44, 53C50, 58J05text