Liu, D., Zhou, S., Gao, J., & Xu, D. (2013). Phosphomolybdic Acid Catalyzed Synthesis of 13-Aryl-5H-dibenzo[b,i]-xanthene-5,7,12,14(13H)-tetraones. Asian Journal of Chemistry, 25(14), 7864–7866. https://doi.org/10.14233/ajchem.2013.14660