[1] GeoDynApp ECSING Grp, Madrid, Spain
[2] Univ Santiago de Compostela, Dept Matemat, Rua Lope Gomez de Marzoa, E-15782 Santiago De Compostela, Spain
[3] Univ Rennes 1, Inst Rech Math Rennes, F-35042 Rennes, France
[4] Univ Republica, Fac Ingn, Inst Matemat & Estadst Rafael Laguard, J Herrera y Reissig 565, Montevideo 11300, Uruguay
[5] Univ Nacl Autonoma Mexico, Apartado Postal 273,Admon Correos 3, Cuernavaca 62251, Morelos, Mexico