Williams, I.O., R.S. Parker, and J. Swanson. “Vitamin A Content of Southeastern Nigerian Vegetable Dishes, Their Consumption Pattern and Contribution to Vitamin A Requirement of Pregnant Women in Calabar Urban, Nigeria”. Pakistan Journal of Nutrition 8, no. 7 (June 15, 2009): 1000–1004. Accessed September 4, 2025. https://pjnonline.org/pjn/article/view/935.