Khazaei, Ardeshir, et al. “SnCl2·2H2O and Ni(OAc)2&Middot;4H2O: Efficient Heterogeneous Inorganic Catalysts for the Chemoselective Synthesis of Geminal Diacetates (Acylal) Under Solvent-Free Conditions”. Asian Journal of Chemistry, vol. 23, no. 2, Oct. 2010, pp. 627-30, https://asianpubs.org/index.php/ajchem/article/view/15861.