Gopalakrishnan, M., et al. “Michael Addition Reaction of Some 3,3-Dimethyl-2,6-Diarylpiperidin-4-Ones”. Asian Journal of Chemistry, vol. 20, no. 8, Mar. 2010, pp. 6241-5, https://asianpubs.org/index.php/ajchem/article/view/12967.