Thi Ngoc Le, Nguyen, and Le Van Tan. “Spectroscopic and Structural Studies on the Complex of Benzoic Acid Azo PhenylCalix[4]arene (BAPC) With Ce4+”. Asian Journal of Chemistry, vol. 24, no. 5, Jan. 2012, pp. 2324-8, https://asianpubs.org/index.php/ajchem/article/view/9011.