Deterministic ascending tree automata I. - J. Virágh (Acta Cybern., 1980)

Deterministic ascending tree automata II. - J. Virágh (Acta Cybern., 1983)

Homomorphic Realizations of Automata with Compositions. - Zoltán Ésik; Pál Dömösi; Ferenc Gécseg; J. Virágh (MFCS, 1986)

On products of automata with identity. - Zoltán Ésik; J. Virágh (Acta Cybern., 1986)

A note on α0* - products of aperiodic automata. - Zoltán Ésik; J. Virágh (Acta Cybern., 1987)