Abstract:
Author's abstract of a dissertation for the degree of Doctor of Physicomathematical Sciences. The dissertation was defended on Oct. 21, 1977, at a session of the Specialized Council D 002.38.02 at the V. A. Steklov Mathematics Institute of the Academy of Sciences of the USSR. Official opponents: Academician of the Academy of Sciences of the USSR, Doctor of Physicomathematical Sciences A. V. Pogorelov; Professor, Doctor of Physicomathematical Sciences É. G. Poznyak; Professor, Doctor of Physicomathematical Sciences A. S. Fedenko.