European Journal of Combinatorics
Good and semi-strong colorings of oriented planar graphs
Information Processing Letters
Gro¨tzsch's 3-color theorem and its counterparts for the torus and the projective plane
Journal of Combinatorial Theory Series B
Journal of Combinatorial Theory Series B - Special issue: dedicated to Professor W. T. Tutte on the occasion of his eightieth birthday
Homomorphisms of Edge-Colored Graphs and Coxeter Groups
Journal of Algebraic Combinatorics: An International Journal
Colored homomorphisms of colored mixed graphs
Journal of Combinatorial Theory Series B
Universal H-colorable graphs without a given configuration
Discrete Mathematics
Homomorphisms and edge-colourings of planar graphs
Journal of Combinatorial Theory Series B
Journal of Combinatorial Theory Series B
K5-free bound for the class of planar graphs
European Journal of Combinatorics - Special issue on Eurocomb'03 - graphs and combinatorial structures
Homomorphisms and edge-colourings of planar graphs
Journal of Combinatorial Theory Series B
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A class C of graphs is said to be H-bounded if each graph in the class C admits a homomorphism to H. We give a general necessary and sufficient condition for the existence of bounds with special local properties. This gives a new proof of the Häggkvist-Hell theorem [R. Häggkvist, P. Hell, Universality of A-mote graphs, European J. Combin. 14 (1993) 23-27] and implies several cases of the existence of triangle free bounds for planar graphs.