Notas de Matemática - Nº 259 http://www.saber.ula.ve/handle/123456789/4764 2007 Tue, 09 Jun 2026 11:59:32 GMT 2026-06-09T11:59:32Z Notas de Matemática http://www.saber.ula.ve/handle/123456789/22785 Notas de Matemática Fri, 29 Feb 2008 09:00:00 GMT http://www.saber.ula.ve/handle/123456789/22785 2008-02-29T09:00:00Z Properties and relations between visibility and illumination operators. http://www.saber.ula.ve/handle/123456789/22786 Properties and relations between visibility and illumination operators. Formica, Alberto; Rodríguez, Mabel Mon, 18 Feb 2008 09:00:00 GMT http://www.saber.ula.ve/handle/123456789/22786 2008-02-18T09:00:00Z