1. Instituto Politécnico Nacional - CITEDI, Instituto Politécnico Nacional 1310, Mesa de Otay, Tijuana B.C. 22435, Mexico
2. CICESE, Department of Computer Science, Carretera Ensenada-Tijuana 3918, Ensenada B.C. 22860, MexicocChelyabinsk State University, Department of Mathematics, 129 Bratiev Kashirinikh, 454001, Russia
3. Universidad Rey Juan Carlos, Calle Tulipán S/N 28933 Móstoles, Madrid, Spain