Daniel Ramos Javier Gonzalez-Dominguez Doroteo Torre Toledano Joaquin Gonzalez-Rodriguez 1254-1258 2009 Encyclopedia of Biometrics http://dx.doi.org/10.1007/978-0-387-73003-5_203 reference/bio/2009 db/reference/bio/s.html#RamosGTG09