David Onwuchekwa, Ph.D, and Onyemezikeya, Obubeleye George. “TRANSPORTATION MODEL AND COST CONTROL OF PLASTIC MANUFACTURING FIRMS IN PORT HARCOURT”. BW Academic Journal 2 (February 24, 2025): 149–160. Accessed June 27, 2026. https://bwjournal.org/index.php/bsjournal/article/view/2772.