Xie, Youhai, Yingling Wang, and Liqiang Wu. 2011. “One-Pot Synthesis of 7-Alkyl-6H,7H-naphtho[1’,2’:5,6]pyrano[3,2-c]chromen-6-Ones in Presence of Alum”. Asian Journal of Chemistry 23 (12):5377-80. https://asianpubs.org/index.php/ajchem/article/view/11155.