ابراهيم سميرة خليل. “The Use of Replacement Models On Determine the Optimal Time to Replacement”. Journal of Economics and Administrative Sciences 19, no. 72 (September 1, 2013): 321. Accessed July 7, 2025. https://www.jeasiq.uobaghdad.edu.iq/index.php/JEASIQ/article/view/952.