Qingyan He Xinge You Limin Cui Zaochao Bao Watermarking technique based on discrete non-separable wavelet filters. 3577-3582 2007 SMC http://dx.doi.org/10.1109/ICSMC.2007.4414226 conf/smc/2007 db/conf/smc/smc2007.html#HeYCB07