Príncipe, M., Suárez, H., Jimenez-Aleman, G. H., Martínez, R., & Spange, S. (2007). Composites prepared from silica gel and furfuryl alcohol with p-toluenesulfphonic acid as the catalyst. Polymer Bulletin, 58(4), 619. doi:10.1007/s00289-006-0701-5.