Hiroaki Inayoshi Takio Kurita Binarizing Training Samples with Multi-threshold for Viola-Jones Face Detector. 588-597 2007 ICONIP (2) http://dx.doi.org/10.1007/978-3-540-69162-4_61 conf/iconip/2007-2 db/conf/iconip/iconip2007-2.html#InayoshiK07