Cancellative actions
The following problem is considered: when can the action of a cancellative semigroup on a set be extended to a simply transitive action of the universal group of on a larger set.
Categories of Semigroups with Divisor Theory
Characterization of monoids by condition (P) of cyclic left acts.
Closure operations and semigroups of quotients
Cohomology groups of a groupoid.
Colimits of representable algebra-valued functors.
Commutative semigroup cohomology.
Commutative semigroups with few fully invariant congruences I.
Commutative semigroups with few fully invariant congruences II.
Complementation and inner automorphism regular semigroups.
Completely quasi-projective monoids.
Completions and injective hulls of E-reflexive inverse semigroups.
Completions for partially ordered semigroups.
Congruence relations on left canonic semigroups.
Constructing inverse monoids from small categories.
Construction and representation of regular semigroups.
Correction and supplement to "On a pull-back diagram for orthodox semigroups".
Crossed semimodules and Schreier internal categories in the category of monoids.