1. V. I. Ogievetskii and L. Mezinchesku, Usp. Mat. Nauk,117, No. 4, 637?700 (1975).
2. F. A. Berezin and D. A. Leitis, Dokl. Akad. Nauk SSSR,224, No. 3, 505?508 (1975).
3. F. A. Berezin, Mat. Zametki,1, No. 3, 269?276 (1967).
4. I. N. Bernshtein and D. A. Leitis, Funkts. Anal. Prilozhen.,11, No. 1, 55?56 (1976).
5. D. A. Leitis, Usp. Mat. Nauk,29, No. 3, 209?210 (1974).