Kazuya Ueki Teruhide Hayashida Tetsunori Kobayashi Two-dimensional Heteroscedastic Linear Discriminant Analysis for Age-group Classification. 585-588 2006 conf/icpr/2006 ICPR (2) http://doi.ieeecomputersociety.org/10.1109/ICPR.2006.1138 db/conf/icpr/icpr2006-2.html#UekiHK06