Abd El-Aziz, A. A. “An Extended Data Protection Model Based on Cipher-Text-Policy Attribute Based Encryption Model and an XACML Framework in Cloud Computing”. International Journal of Advanced Science and Technology, Vol. 28, no. 16, Dec. 2019, pp. 1021 -33, http://sersc.org/journals/index.php/IJAST/article/view/2048.