GUMRUKCU, GULSAH, et al. “Extraction of Anthocyanin Pigments from Red Onion (AlliumcepaL.) and Dyeing Woolen Fabrics”. Asian Journal of Chemistry, vol. 20, no. 4, Mar. 2010, pp. 2891-02, https://asianpubs.org/index.php/ajchem/article/view/12659.