Statistical convergence of subsequences of a given sequence. Mačaj, M.; Šalát, T. — 2001 Mathematica Bohemica
On a class of densities of sets of positive integers. Mačaj, M.; Mišík, L.; Šalát, T.; Tomanová, J. — 2003 Acta Mathematica Universitatis Comenianae. New Series