Bhagwat, V.W., et al. “QSPR Evidences for Topological Indices to Mimic Lipophilicity of Thia and Aza-Crown Ethers”. Asian Journal of Chemistry, vol. 21, no. 7, Mar. 2010, pp. 5212-20, https://asianpubs.org/index.php/ajchem/article/view/18295.