Gunasekaran1, B., et al. “Synthesis and Crystal Structure of Methyl 9-(4-Methoxyphenyl)-8a,9,9a,10,11,12,13,14a-Octa Hydro-8H-benzo[f]chromeno[3,4-b]indolizine-8a-Carboxylate”. Asian Journal of Chemistry, vol. 25, no. 20, May 2013, pp. 51-54, https://asianpubs.org/index.php/ajchem/article/view/25_Supplementary%20Issue_14.