Recursive inseparability of the sets of identically valid and finitely refutable formulas of some elementary theories of varieties.
Rees ideal algebras
We describe algebras and varieties for which every ideal is a kernel of a one-block congruence.
Refinement Monoids, Vaught Monoids, and Boolean Algebras.
Reflexive relations and Mal'tsev conditions for congruence lattice identities in modular varieties
Reg-strongly solid varieties of commutative semigroups
Regularity and permutability via transferability of tolerances
Regularity in arithmetical varieties
Regularity of algebras with applications to congruence class geometry
Relation products of congruences and factor congruences
Relational characterizations of permutable and -permutable varieties
Relative congruence distributivity within quasivarieties of nearly associative Φ-algebras
Relatively free *-bands.
Relatively free lattices
Relatively pseudocomplemented directoids
The concept of relative pseudocomplement is introduced in a commutative directoid. It is shown that the operation of relative pseudocomplementation can be characterized by identities and hence the class of these algebras forms a variety. This variety is congruence weakly regular and congruence distributive. A description of congruences via their kernels is presented and the kernels are characterized as the so-called -ideals.
Remarks on C-independence in Cartesian products of abstract algebras
Remarks on equational theories of semilattices with operators
Remarks on -independence of Stone algebras
Remarks on quasivarieties of algebras
Remarks on tolerance algebras
Représentations matricielles des séries d'arbre reconnaissables