N. Ahmed Wazzan, “DFT and MP2 Study of Geometry, IR and UV-Visible Spectroscopy and First Hyperpolarizability of 2-Aminopyridine, 3-Aminopyridine and 4-Aminopyridine in Gas Phase and in Solvents”, ajc, vol. 27, no. 12, pp. 4641–4656, Aug. 2015.