Rezaei, Ramin, and Mozhdeh Shakeri. “A Mild and Efficient Method for Synthesis of B-Enaminones Using Melamine-Formaldehyde Resin Supported H+ Under Solvent Free Conditions”. Asian Journal of Chemistry, vol. 25, no. 13, July 2013, pp. 7079-82, doi:10.14233/ajchem.2013.14436.