1. R.T. Sanderson: Chemical Periodicity, Reinhold Publ. Co., New York, NY, 1964, pp. 31–39.
2. J. Terpiłowski, E. Zaleska, and W. Gaweł: Roczniki Chem. (Ann. Soc. Chim. Pol.), 1965, vol. 39, pp. 1367–75 (in Polish).
3. Y. Nakamura and M. Shimoji: Trans. Faraday Soc., 1971, vol. 67, pp. 1270–77.
4. J. Terpiłowski, W. Gaweł, and A. Bogacz: Roczniki Chem. (Ann. Soc. Chim. Pol.), 1972, vol. 46, pp. 3–8 (in Polish).
5. M.M. Asadov, M.B. Babanly, and A.A. Kuliev: Izv. AN SSSR, Neorg. Mater., 1977, vol. 13, pp. 1407–10 (in Russian).