Dongyan Liu Wenbo Liu Gong Zhang An Adaptive Watermarking Scheme Based on Nonsubsampled Contourlet Transform for Color Image Authentication. 748-752 2008 ICYCS http://dx.doi.org/10.1109/ICYCS.2008.61 conf/icycs/2008 db/conf/icycs/icycs2008.html#LiuLZ08