Let F be an infinite field and UT(d(1),..., d(n)) be the algebra of upper block-triangular matrices over F. In this paper we describe a basis for the C-graded polynomial identities of UT(d(1),..., d(n)), with an elementary ...

For every positive integer N >= 2 we consider the linear differential centre (x) over dot = Ax in R-4 with eigenvalues +/- i and +/- Ni. We perturb this linear centre inside the class of all polynomial differential systems ...

For any finite commutative ring B with an identity there is a strict inclusion B[X; Z(0)] subset of B[X; Z(0)] subset of B[X; 1/2(2)Z(0)] of commutative semigroup rings. This work is a continuation of Shah et al. (2011) ...