On the problem of freeness of multiplicative matrix semigroups. - Pawel Gawrychowski; Marin Gutan; Andrzej Kisielewicz 001 (Theor. Comput. Sci., 2010)

Relations in the semigroup of 2 × 2 upper-triangular matrices. - Henri-Alex Esbelin; Marin Gutan (Int. J. Algebra Comput., 2020)