Volume 20, No. 2 (1984)

Branching of Singularities for Degenerate Hyperbolic Operators

On the $XY$-Model on Two-Sided Infinite Chain

$\overline{\partial }$ Cohomology of $(H,C)$-Groups

The Riemann–Hilbert Problem for Holonomic Systems

Theory of Multiple Polynomial Remainder Sequence

Continuous Cohomologies of Lie Algebras of Formal $G$-Invariant Vector Fields and Obstructions to Lifting Foliations