Sohal, Harvinder Singh, et al. “One-Pot, Multicomponent Synthesis of Symmetrical Hantzsch 1,4-Dihydropyridine Derivatives Using Glycerol As Clean and Green Solvent”. European Journal of Chemistry, vol. 5, no. 1, Mar. 2014, pp. 171-5, doi:10.5155/eurjchem.5.1.171-175.943.