Pandey, H.K., Gourav Chawla, and Seema Gakhar. 2010. “Spectrophotometric Characterization of Some Doped Pr(III) Systems With O, N and S Containing Ligands”. Asian Journal of Chemistry 18 (4):2925-28. https://asianpubs.org/index.php/ajchem/article/view/20710.