Salih, Abdulkareem, and Salih Mahmood. “Digital Color Image Watermarking Using Encoded Frequent Mark”. Journal of Engineering 25, no. 3 (February 28, 2019): 81-88. Accessed August 15, 2020. http://joe.uobaghdad.edu.iq/index.php/main/article/view/j.eng.2019.03.07.