Hegazy, Maha Abdel Monem, et al. “Spectral Resolution and Simultaneous Determination of Oxymetazoline Hydrochloride and Sodium Cromoglycate by Derivative and Ratio-Based Spectrophotometric Methods”. European Journal of Chemistry, vol. 6, no. 3, Sept. 2015, pp. 319-24, doi:10.5155/eurjchem.6.3.319-324.1278.