Yasuhiro Fujii Ryu Ebisawa Yumiko Togashi Takaaki Yamada Yoshinori Honda Seiichi Susaki Third-party approach to controlling digital copiers. 686-688 2008 iiWAS http://doi.acm.org/10.1145/1497308.1497444 conf/iiwas/2008 db/conf/iiwas/iiwas2008.html#FujiiETYHS08