Renqvist, U. H., A. C. De Vreeze, and B. Evenhuis. “The Effect of Traditional Cooking Methods on Carotene Content in Tropical Leafy Vegetables”. The Indian Journal of Nutrition and Dietetics, vol. 15, no. 5, May 1978, pp. 154-8, https://informaticsjournals.co.in/index.php/ijnd/article/view/12207.