Tappayuthpijarn, P., Q. Dejatiwongse Na Ayudhya, P. Pongpetch, and A. Leelaporn. “Antibacterial Activity of Extracts of Piper Betle Leaf”. Journal of Basic and Applied Pharmacology, vol. 4, no. 4, July 2015, pp. 205-12, https://li01.tci-thaijo.org/index.php/JBAP/article/view/36773.