Computer Science Dept., Faculty of Company-Linked Programmes, Berlin School of Economics and Law, Berlin, Germany, November 2010.
Instituto Nacional de Astrofísica, Óptica, Electrónica, INAOEP, Tonantzintla, Puebla, México, October 2009, January 2010.
Centro de Estadística y Software Matemático (CESMa), Universidad Simón Bolívar, December 1995-January 1996
Department of Computer Science, University of Bayreuth, Bayreuth, Germany, June 1995