1. V. E. Plyushchev, L. P. Shklover and M. Shkol'nikov, Zh. Strukt. Khimii,5 794 (1964).
2. J. Mayer, M. Steinberg, F. Feigenblatt, and A. Glasner, J. Phys. Chem.,66, 1737 (1962).
3. V. E. Plyushchev, L. P. Shklover, and T. A. Trushina, Zh. Neorgan. Khimii,9, 2710 (1964).