Mae Reyes Aribon-Libag , Christle. “Billing and Online Payment Portal With Multi-Factor Authentication Using One-Time Password”. Journal of Advanced Computer Science & Technology (JACST) 12, no. 1 (January 6, 2024): 1–18. Accessed December 22, 2024. https://sciencepubco.com/index.php/JACST/article/view/32435.