N. Uchegbu, T. Nnamocha, and C. Ishiwu, “Natural Food Colourants Juxtaposed with Synthetic Food Colourant: A Review”, Pak. J. Nutr., vol. 19, no. 8, pp. 404–419, Jul. 2020, doi: 10.3923/pjn.2020.404.419.