Partial orders and their semigroups of closed relations.
Partial orders, closed relations and their automorphisms.
p-congruences on p-regular semigroups.
Perfect completely semisimple inverse semigroups.
Perfectness of certain subsemigroups of a perfect semigroup.
Periodic endomorphisms of a free monoid.
Permutable duo semigroups.
Polynomial functions over commutative semigroups.
Polynomial functions over monoids.
Positive definite functions on Abelian semigroups
Positive definite functions on discrete commutative semigroups.
Positive functions from -indecomposable semigroups into partially ordered sets
Positive-definite functions on discrete commutative semigroups: Errata and supplements.
Primitive orthodox semigroups.
Properties of congruences on commutative monoids.