Ginting, Mega, and Francka Lee. “Design and Implementation of a Stock Purchase System for Printing Businesses Using the Waterfall Method”. Journal of Information Systems and Informatics 7, no. 2 (June 23, 2025): 1023-1041. Accessed February 4, 2026. https://journal-isi.org.adsii.or.id/index.php/isi/article/view/1057.