Mohsen Ashourian Reza Enteshari Jeonghee Jeon Digital Watermarking of Three-Dimensional Polygonal Models in the Spherical Coordinate System. 590-593 2004 conf/cgi/2004 Computer Graphics International http://doi.ieeecomputersociety.org/10.1109/CGI.2004.1309270 db/conf/cgi/cgi2004.html#AshourianEJ04