YANG, CHING YU, and Chi-Kai Huang. “Nearly Reversible ECG Steganography Based on Polar Coordinate System With Digital Replacement Technique”. Transactions on Machine Learning and Artificial Intelligence 9, no. 6 (November 20, 2021): 9–19. Accessed January 23, 2022. https://journals.scholarpublishing.org/index.php/TMLAI/article/view/11177.