Ibrahim M. Ibrahim Sherif Hazem Nour El-Din Abdel Fatah A. Hegazy An Effective and Secure Buyer-Seller Watermarking Protocol. 21-28 2007 IAS http://doi.ieeecomputersociety.org/10.1109/IAS.2007.17 conf/IEEEias/2007 db/conf/IEEEias/IEEEias2007.html#IbrahimEH07