Ayad, Magda Mohamed, et al. “Application of 4-Chloro-7-Nitrobenzofurazan for the Analysis of Propafenone and Diltiazem Hydrochlorides Using Kinetic Spectrophotometric and Spectrofluorimetric Methods”. European Journal of Chemistry, vol. 4, no. 1, Mar. 2013, pp. 35-43, doi:10.5155/eurjchem.4.1.35-43.713.