Darugar, Vahidreza, et al. “Application of Hammett Equation to Intramolecular Hydrogen Bond Strength in Para-Substituted Phenyl Ring of Trifluorobenzoylacetone and 1-Aryl-1,3-Diketone Malonates”. European Journal of Chemistry, vol. 9, no. 3, Sept. 2018, pp. 213-21, doi:10.5155/eurjchem.9.3.213-221.1713.