Narendra Sukma, F. B. S. A., Y. Purnomo, and M. Sodikin. “Enhancing Customer Loyalty Through Service Quality: A Congruity Value Theory Perspective in Indonesian Postal Services”. IJUS | International Journal of Umranic Studies, vol. 7, no. 2, July 2024, pp. 7-14, https://unissa.edu.bn/journal/index.php/ijus/article/view/934.