Henderi, Didik Setiyadi, Dian Sugiarto, Abas Sunarya. “A Proposed Model for Sales Data Warehouse Using Nine-Step Design ”. International Journal of Advanced Science and Technology, Vol. 29, no. 7, July 2020, pp. 12922 -31, http://sersc.org/journals/index.php/IJAST/article/view/28882.