Farghaly, Thoraya Abd El-Reheem, et al. “Study on Regioselective Synthesis of Bioactive Bis-Spiropyrazolines Using Molecular Orbital Calculations”. European Journal of Chemistry, vol. 5, no. 4, Dec. 2014, pp. 577-83, doi:10.5155/eurjchem.5.4.577-583.1039.