Yong Ma Xiaoqing Ding Face Detection Based on Hierarchical Support Vector Machines. 222-225 2002 conf/icpr/2002 ICPR (1) https://doi.org/10.1109/ICPR.2002.1044659 https://doi.ieeecomputersociety.org/10.1109/ICPR.2002.1044659 db/conf/icpr/icpr2002-1.html#MaD02