Conditions for the mean square stability of linear stochastic differential-difference equations of the neutral type in the critical case are obtained.

The limit theorems for the solutions of linear matrix differential equations in the Sobolev’s Wn,p-norms are established. The case of the uniform C-norm was studied earlier by many authors in detail. Some applications are given.

The wave equation for a non-homogeneous string on a segment is considered. The right end point is .xed. On the left end point, L^∞-control that is bounded by a given constant is considered. Necessary and su.cient conditions ...