Roberto Paredes Palacios Enrique Vidal Daniel Keysers An Evaluation of the WPE Algorithm Using Tangent Distance. 48-51 2002 ICPR (4) http://doi.ieeecomputersociety.org/10.1109/ICPR.2002.1047397 db/conf/icpr/icpr2002-4.html#PalaciosVK02