Approximation Numbers of the Two-Dimensional Rectangular Hardy OperatorUpper and lower bounds are obtained for the approximation numbers of the
two-dimensional Two-dimensional reductions of the cone of positive diagonal operators in ℓ2 that there is no
two-dimensional orthoprojector in the Hilbert
space l2 for which the reduction of the cone of positive
Partition of a unity on infinite-dimensional manifold of the Lipschiz class Lipk for infinitedimensional manifold M modeled in nonnormable topological vector Fréchet
space F. We establish that a manifold
Initial-boundary value problems for two dimensional Kawahara equation of boundary conditions for the generalized
two-dimensional Kawahara equation with nonlinearity of higher order