E-minimal semigroups.
Endliche Gruppen mit vielen Untergruppen.
Equivalence relations defined by automorphism groups
Equivalence Systems with Finitely Many Relations.
Equivalences, a-semigroups and a-congruences.
Etude du treillis des congruences à droite sur le monoide bicyclique.
E-varieties of regular semigroups, relatively bifree objects and fully invariant congruences.
Every at most four element algebra has a Mal'cev theory for permutability
Exchange properties and basis properties for closure operators
Existence and uniqueness of -representations of algebras
Factorable congruences and factorable congruence blocks on powers of a finite algebra
Factorable congruences and strict refinement.
Factor-union representation of phenotype systems.
Families of strongly projective graphs
We give several characterisations of strongly projective graphs which generalise in many respects odd cycles and complete graphs [7]. We prove that all known families of projective graphs contain only strongly projective graphs, including complete graphs, odd cycles, Kneser graphs and non-bipartite distance-transitive graphs of diameter d ≥ 3.
Fast algorithms for finding a subdirect decomposition and interesting congruences of finite algebras
Finite hull systems and their implication bases. (Endliche Hüllensysteme und ihre Implikationenbasen.)
Finitely generated relations and their applications to permutable and -permutable varieties
Formal Translation Monoid and Algebra Congruences in a Monodial Category.
Four-part semigroups - semigroups of Boolean operations
Four-part semigroups form a new class of semigroups which became important when sets of Boolean operations which are closed under the binary superposition operation f + g := f(g,...,g), were studied. In this paper we describe the lattice of all subsemigroups of an arbitrary four-part semigroup, determine regular and idempotent elements, regular and idempotent subsemigroups, homomorphic images, Green's relations, and prove a representation theorem for four-part semigroups.
Free groupoids with axioms of the form and/or .