Study of electronic spectra of free-base porphin and Mg-porphin: comprehensive comparison of variety of ab initio, DFT, and semiempirical methods.
Seda J, Burda JV, Leszczynski J. Study of electronic spectra of free-base porphin and Mg-porphin: comprehensive comparison of variety of ab initio, DFT, and semiempirical methods. J Comput Chem. 2005 Feb; 26(3):294-303.