Wu, L. et al. 2010. Silica Supported Perchloric acid (HClO4-SiO2) Catalyzed Synthesis of 8,10-Dimethyl- 8,12-dihydro-12-aryl-9H-naphtho- [1’,2’:5,6]pyrano[2,3-d]pyrimidine-9,11(10H)-diones Under Solvent-Free Conditions. Asian Journal of Chemistry. 22, 8 (Jun. 2010), 6178–6184.