Setyadi, Heribertus, Supriyanta Supriyanta, and Galih Nurohim. “Improving Junk Sale and Purchase Transactions Using a Spiral Model-Based System”. Journal of Information Systems and Informatics 6, no. 4 (December 13, 2024): 2237-2254. Accessed December 19, 2025. https://journal-isi.org.adsii.or.id/index.php/isi/article/view/871.