Sarwar, Ghulam, Maqbool H. Sial, and Najam-ul Hassan. “Investment in Education and Income Inequality: Testing Inverted U-Shaped Hypothesis for Pakistan”. Pakistan Journal of Social Sciences 36, no. 2 (December 31, 2016): 751-760. Accessed June 10, 2026. https://pjss.bzu.edu.pk/index.php/pjss/article/view/460.