Akira Horimatsu Ryo Niwa Masakazu Iwamura Koichi Kise Seiichi Uchida Shinichiro Omachi 237-244 2008 Document Analysis Systems https://doi.org/10.1109/DAS.2008.88 https://doi.ieeecomputersociety.org/10.1109/DAS.2008.88 conf/das/2008 db/conf/das/das2008.html#HorimatsuNIKUO08