F. Bamoharram, Fatemeh, et al. “Supported Nano-SiO2 H14[NaP5W30O110] Heteropolyacid: A Green and Reusable Catalyst in Oxidation of Aromatic Aldehydes”. Asian Journal of Chemistry, vol. 24, no. 12, Aug. 2012, pp. 5582-4, https://asianpubs.org/index.php/ajchem/article/view/9938.