On varieties of graphs. - Alfonz Haviar; Roman Nedela (Discuss. Math. Graph Theory, 1998)

All trees of diameter five are graceful. - Pavel Hrnciar; Alfonz Haviar (Discret. Math., 2001)

On varieties of orgraphs. - Alfonz Haviar; Gabriela Monoszová (Discuss. Math. Graph Theory, 2001)

Varieties of Posets. - Alfonz Haviar; Judita Lihová (Order, 2005)