A new proof of Reiterman's theorem
A remark on topological spaces, grids, and topological systems
Algebraic properties of Husimi trees
Decompositions of homomorphisms
Does imply axiom of choice?
Formulas and ultraproducts in categories
Mal'tsev--Neumann products of semi-simple classes of rings
Malt’tsev–Neumann products of semi-simple classes of associative rings are studied and some conditions which ensure that such a product is again a semi-simple class are obtained. It is shown that both products, and of semi-simple classes and are semi-simple classes if and only if they are equal.
Minimal formations of universal algebras
A class ℱ of universal algebras is called a formation if the following conditions are satisfied: 1) Any homomorphic image of A ∈ ℱ is in ℱ; 2) If α₁, α₂ are congruences on A and , i = 1,2, then A/(α₁∩α₂) ∈ ℱ. We prove that any formation generated by a simple algebra with permutable congruences is minimal, and hence any formation containing a simple algebra, with permutable congruences, contains a minimum subformation. This result gives a partial answer to an open problem of Shemetkov and Skiba...
Monotonic valuations and valuations of triads of higher types
On convexities of lattices
On the semidirect product of the pseudovariety of semilattices by a locally finite pseudovariety of groups
On the structure of semilattice sums
Operads and algebraic geometry.
Quasi-radicals and Radicals in Categories
Relational structures and dependence spaces
Retract varieties of monounary algebras
Unequivocal linearly ordered groups
Valuations of structures