Yohanes Chandra, Reffiano Noeris Hiwa , Emil R. Kaburuan*, Gunawan Wang, Sfenrianto. “Applying Block-Chain Based Smart Contract in Payment Management System”. International Journal of Control and Automation, Vol. 13, no. 02, June 2020, pp. 1193 -99, http://sersc.org/journals/index.php/IJCA/article/view/26912.