A. A. M. M. ALGHAIL and S. khaled, “A Secure Online Booking System with OTP for Sultans Spa Resort”, aitcs, vol. 6, no. 1, pp. 663–682, Jul. 2025, Accessed: Aug. 14, 2026. [Online]. Available: https://periodical.uthm.edu.my/index.php/aitcs/article/view/18872