On the parity of planar covers
| Autor: | Dan Archdeacon, R. B. Richter |
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| Rok vydání: | 1990 |
| Předmět: | |
| Zdroj: | Journal of Graph Theory. 14:199-204 |
| ISSN: | 1097-0118 0364-9024 |
| DOI: | 10.1002/jgt.3190140208 |
| Popis: | A covering is a graph map φ: G→H that is an isomorphism when restricted to the star of any vertex of G. If H is connected then |φ −1 (v)| is constant. This constant is called the fold number. In this paper we prove that if G is a planar graph that covers a nonplanar H, then the fold number must be even |
| Databáze: | OpenAIRE |
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