SHEN, J. H., Z. C. WANG, and X. Z. QIAN. “ON EXISTENCE OF POSITIVE SOLUTIONS OF NEUTRAL DIFFERENCE EQUATIONS”. Tamkang Journal of Mathematics 25, no. 3 (September 1, 1994): 257–265. Accessed May 8, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4453.