Tater, P.C., et al. “Variation in Symmetry Around Doped Nd3+ Ion in Saturated Solution of Sulphonalides With Reference to Judd-Ofelt Electronic Spectral Parameter”. Asian Journal of Chemistry, vol. 13, no. 2, Mar. 2010, pp. 801-2, https://asianpubs.org/index.php/ajchem/article/view/22678.