1. A. P. Ivanov and V. A. Loiko, Vestsi Akad. Nauk BSSR, Ser. Fiz.-Mat. Navuk, No. 5, 113 (1971).
2. S. P. Shuvalov, Zh. Fiz. Khim.,8, No. 3, 387 (1936).
3. S. P. Shuvalov, Zh. Fiz. Khim.,8, No. 4, 514 (1936).
4. S. P. Shuvalov, Zh. Fiz. Khim.,11, No. 3, 384 (1938).
5. I. H. Webb, JOSA,38, 1, 27 (1948).