Let ℜ and ℜ′ be alternative rings. In this article we investigate the additivity of surjective elementary maps of ℜ × ℜ′. As a main theorem, we prove that if ℜ idempotent satisfying some conditions, these maps are additive.

We accomplish the classification of Cohen–Macaulay modules over the curve singularities of type T₄₄ and the description of the corresponding matrix factorizations, started in [8].

Semiabelinan flocks and n-ary groups are characterized by the properties of parallelograms and vectors of the affine geometry defined by these flocks and n-ary groups.

Magic rectangles are a classical generalization of the well-known magic squares, and they are related to graphs. A graph G is called degree-magic if there exists a labelling of the edges by integers 1, 2, . . . , |E(G)| ...

In this paper, we initiate the study of Paley-type graphs ГN modulo N = pq, where p, q are distinct primes of the form 4k + 1. It is shown that ГN is an edge-regular, symmetric, Eulerian and Hamiltonian graph. Also, the ...

The aim of this paper investigates some combinatorial characteristics of minimal key and antikey of closure operations. We also give effective algorithms finding minimal keys and antikeys of closure operations. We estimate ...