Y. Xie, Y. Wang, and L. Wu, “One-Pot Synthesis of 7-Alkyl-6H,7H-naphtho[1’,2’:5,6]pyrano[3,2-c]chromen-6-ones in Presence of Alum”, ajc, vol. 23, no. 12, pp. 5377–5380, Sep. 2011.