Ramakrishnappa, Sowmya, Deepa Anbazhagan, Verasingam Kumarasamy, and Vinoth Kumarasamy. “Intra-Individual Variability in Sleep Quality Among Coffee Consumers: A Cross-Sectional Study”. Pakistan Journal of Nutrition 19, no. 3 (February 15, 2020): 146–152. Accessed September 7, 2025. https://pjnonline.org/pjn/article/view/2842.