On problems of B. Choczewski and M. Kuczma concerning an integral equation
On products of additive functions.
On products of additive functions (a third approach).
On properties of solutions for two functional equations arising in dynamic programming.
On quadratic and sesquilinear functionals.
On quadratic forms.
On quasi-continuous iteration groups on the unit circle.
On quasi-continuous iteration semigroups and groups of real functions
On reduction of linear two variable functional equations to differential equations without substitutions.
On regular solutions of functional equations.
On Reproductive Solutions Of Arbitrary Equations
On reproductive solutions of arbitrary equations.
On reverses of some binary operators
The notion of reverse of any binary operation on the unit interval is introduced. The properties of reverses of some binary operations are studied and some applications of reverses are indicated.
On ring derivations and quadratic functionals.
On S. Gołąb's characterization of the anharmonic ratio
On second-order Taylor's series approximation and linear homogeneity.
On separation theorems for subadditive and superadditive functionals
We generalize the well known separation theorems for subadditive and superadditive functionals to some classes of not necessarily Abelian semigroups. We also consider the problem of supporting subadditive functionals by additive ones in the not necessarily commutative case. Our results are motivated by similar extensions of the Hyers stability theorem for the Cauchy functional equation. In this context the so-called weakly commutative and amenable semigroups appear naturally. The relations between...
On series-like iterative equation with a general boundary restriction.
On several classes of sets II.
On simultaneous Abel equations.