S. Okdeh, Malek, et al. “Determination of P-Amino Benzoic Acid and P-Hydroxy Methyl Benzoate in Sunscreens by HPLC ”. Asian Journal of Chemistry, vol. 15, no. 2, Mar. 2010, pp. 664-7, https://asianpubs.org/index.php/ajchem/article/view/21663.