D. I. G. Hutasuhut, Ommi Alfina, Nita Syahputri, S. F. Sihotang, Efani Desi, and Siti Aliyah, “Expert System Detects Boiler Engine Damage Using Certainty Factors”, u-net, vol. 5, no. 2, pp. 52-59, Feb. 2021.