2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/36298We report on the cited papers refs. 1 - 18 from the following points of view: What do we exactly know about solutions when no exact solution (in the sense of "solution in closed form") is available? In which sense do these solutions possess a singularity? In which cases do conformal relations and/or dimensional reductions simplify the deduction? Furthermore, we outline some open questions worth of being studied in future research.5 pages, LaTeX sprocl style, no figures, to appear in Proceedings of the International Seminar on Mathematical Cosmology, Potsdam March 30 - April 4, 1998, M. Rainer and H.-J. Schmidt (eds.), World Scientific PC SingaporeGeneral Relativity and Quantum Cosmologytext