Pandey, H.K., G.K. Joshi, and S.S. Shrimali. 2010. “Electronic Spectral Characterization of Pr(III) Systems Involving Sulphonanilide Environment in DMF Medium”. Asian Journal of Chemistry 11 (4):1418-22. https://asianpubs.org/index.php/ajchem/article/view/23504.