ISSN 1234-3099 (print version)

ISSN 2083-5892 (electronic version)

Discussiones Mathematicae Graph Theory

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Discussiones Mathematicae Graph Theory


Discussiones Mathematicae Graph Theory 21(1) (2001) 207-221
DOI: 10.7151/dmgt.1144


Alfonz Haviar and Gabriela Monoszová

Department of Mathematics, Faculty of Natural Sciences
Matej Bel University, Tajovského 40, 974 01
Banská Bystrica, Slovakia


In this paper we investigate varieties of orgraphs (that is, oriented graphs) as classes of orgraphs closed under isomorphic images, suborgraph identifications and induced suborgraphs, and we study the lattice of varieties of tournament-free orgraphs.

Keywords: orgraph, variety, lattice.

2000 Mathematics Subject Classification: 05C20.


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Received 13 November 2000
Revised 16 May 2001