1. A. T. Balaban, A. Dinculescu, G. N. Dorofeenko, G. W. Fischer, A. V. Koblik, V. V. Mezheritskii and W. Schroth, in Adv. Heterocycl. Chem., Suppl. 2, Academic Press, New York, 1982.
2. Benzo[c] Pyrlium Salts: Syntheses, Reactions, and Physical Properties