V. Blanco, P. Gonzalez, J. C. Cabaleiro, D. B. Heras,
T. F. Pena, J. J. Pombo and F. F. Rivera
*Department of Statistics and Computer Science
La Laguna University
38071 Tenerife, Spain
+Department of Electronics and Systems
A Coru?a University
15071 A Coru?a, Spain
Department of Electronics and Computer Science
Santiago de Compostela University
15782 Santiago, Spain