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 19(1) (1999) 5-11
DOI: 10.7151/dmgt.1081


Stefan Grünewald

Universität Bielefeld, Fakultät für Mathematik
Postfach 100131, 33501 Bielefeld, Germany

Eckhard Steffen

Princeton University
Program in Applied and Computational Mathematics
Fine Hall, Washington Road
Princeton, New Jersey 08544-1000, USA



Snarks are bridgeless cubic graphs with chromatic index χ′ = 4. A snark G is called critical if χ′(G-{v,w}) = 3, for any two adjacent vertices v and w.

For any k ≥ 2 we construct cyclically 5-edge connected critical snarks G having an independent set I of at least k vertices such that χ′(G-I) = 4.

For k = 2 this solves a problem of Nedela and Skoviera [6].

Keywords: cubic graphs, snarks, edge colorings.

1991 Mathematics Subject Classification: 05C15, 05C70.


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Received 24 November 1997
Revised 21 December 1998