MEI, LUO, et al. “The Catalytic Behaviour of Rare Earth Complexes Containing Piperonal Dimethyl Acetal and Dicyclopentadienyl ”. Asian Journal of Chemistry, vol. 15, no. 1, Mar. 2010, pp. 259-62, https://asianpubs.org/index.php/ajchem/article/view/21594.