Li, Mei, et al. “Primary-Secondary Wavelengths Spectrophotometric Determination of Trace Amounts of Cadmium With 2,4-Dibromo-6-Carboxy-Benzenediazoaminoazobenzene ”. Asian Journal of Chemistry, vol. 13, no. 3, Mar. 2010, pp. 1089-96, https://asianpubs.org/index.php/ajchem/article/view/22741.