On best proximity pair theorems and fixed-point theorems.
On best simultaneous approximation.
On Borel Classes of Sets of Fréchet Subdifferentiability
We study possible Borel classes of sets of Fréchet subdifferentiability of continuous functions on reflexive spaces.
On Borel measurability of orbits
On Borel-measurable collections of countable-dimensional sets
On boundaries of parallelizable regions of flows of free mappings.
On cardinalities of row spaces of Boolean matrices.
On Caristi's fixed point theorem in F-type topological spaces.
On certain groups of functions.
On characterizations of fixed points.
On characterized subgroups of Abelian topological groups and the group of all -valued null sequences
Let be an Abelian topological group. A subgroup of is characterized if there is a sequence in the dual group of such that . We reduce the study of characterized subgroups of to the study of characterized subgroups of compact metrizable Abelian groups. Let be the group of all -valued null sequences and be the uniform topology on . If is compact we prove that is a characterized subgroup of if and only if , where and is a finite Abelian group. For every compact Abelian...
On Ciric's fixed point theorem
On Ćirić's non-unique fixed points
On clopen sets in Cartesian products
The results concern clopen sets in products of topological spaces. It is shown that a clopen subset of the product of two separable metrizable (or locally compact) spaces is not always a union of clopen boxes. It is also proved that any clopen subset of the product of two spaces, one of which is compact, can always be represented as a union of clopen boxes.
On cluster sets of arbitrary functions
On coincidence and common fixed points of nearly densifying mappings.
On coincidence and fixed-point theorems in symmetric spaces.
On coincidence theorems for a family of mappings in convex metric spaces.
On common fixed and periodic points of commuting functions.
On common fixed point theorem of four mappings.