A.Gokul, and N.Zahira Jahan. “Secure Mobile Payment Transaction Scheme Using Optimistic Fair Exchange (OFE) Protocols With TPA Model”. International Journal of Intellectual Advancements and Research in Engineering Computations, vol. 7, no. 1, Mar. 2019, pp. 762-8, https://ijiarec.com/ijiarec/article/view/1004.