## Abstract The circular chromatic number is a refinement of the chromatic number of a graph. It has been established in [3,6,7] that there exists planar graphs with circular chromatic number __r__ if and only if __r__ is a rational in the set {1} ∪ [2,4]. Recently, Mohar, in [1,2] has extended the
On the planarity of bicolored digraph grammar systems
✍ Scribed by Anca Pascu; Gheorghe Păaun
- Publisher
- Elsevier Science
- Year
- 1979
- Tongue
- English
- Weight
- 277 KB
- Volume
- 25
- Category
- Article
- ISSN
- 0012-365X
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📜 SIMILAR VOLUMES
The Ferrer-s dimension of a digraph has been shown to be an extension of the order dimension. By proving a property of (finite) transitive Ferrers digraphs, we give an original proof of this above result and derive Ore's alternative definition of the order dimension. Still, the order dimension is pr
For a digraph G = (V, E) let w(G n ) denote the maximum possible cardinality of a subset S of V n in which for every ordered pair It is also shown that for every n there is a tournament T on 2n vertices whose capacity is at least √ n, whereas the maximum number of vertices in a transitive subtourna
Angew,. Chem. In[. Ed. Engl. 24 (198s) 810-816 [\*\*] Copyright 0 The Nobel Foundation 198S.-We thank the Nobel ~-Foundation, Stockholm, for permission to publish this article. ing. 8 16 0 VCH Verlugsgesellschafi mbH, 0-6940 Wernheim. 1985