Fhid, Dr. Omran. “Tri and Tetra Cyclic Theophylline Derivatives As a Potential Agents Acting on CNS and CVS An Overview”. International Journal of Pharmaceutical & Biological Archive 3, no. 3 (July 18, 2012). Accessed April 30, 2025. http://mail.ijpba.info/index.php/ijpba/article/view/661.