CHO, Y. J., N. J. HUANG, and L. XIANG. “COINCIDENCE THEOREMS IN COMPLETE METRIC SPACES”. Tamkang Journal of Mathematics 30, no. 1 (March 1, 1999): 1–7. Accessed November 21, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4191.