Zeng, Wulan. “Synthesis and Crystal Structure of 3-(3,4-Dimethylbenzylidene)-1,5-dioxaspiro[5.5]undecane-2,4-Dione”. Asian Journal of Chemistry, vol. 23, no. 9, June 2011, pp. 4145-7, https://asianpubs.org/index.php/ajchem/article/view/10836.