2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/33537Space-times admitting an $r$-parameter Lie group of homotheties are studied for $r > 2$ devoting a special attention to those representing perfect fluid solutions to Einstein's field equations.Latex 5 pages. Published in: Relativistic Astrophysics and Cosmology". Edt. J. Buitrago, E. Mediavilla and Oscoz; World Scientific. pp. 211-215 (1997)General Relativity and Quantum Cosmologytext