1. M. D. Hollenberg, J. Med. Chem.,331275(1990).
2. J. Moir, J. Chem. Min. Soc. S.A., 98, 335 (1909).
3. J. Moir, Chem. News, 124,105, 118, 133, 149 (1922).
4. O. Hinsberg, J. Prakt. Chem., 93,302 (1916); 94, 179 (1916).
5. W. Hückel, Z. Elektrochem., 27, 305 (1921).