Gyun Lee, Yong, Sung Tae Kim, Dai Il Jung, and Jung Tai Hanh. 2015. “Synthesis and Acid Catalytic Activity of 1,5,3,7-Diazadiphosphocine-1,5-Dicarboxylic Acids”. Asian Journal of Chemistry 27 (4):1481-83. https://doi.org/10.14233/ajchem.2015.18518.