# Gallai–Hasse–Roy–Vitaver theorem

> duality of graph colorings and orientations

**Wikidata**: [Q5518852](https://www.wikidata.org/wiki/Q5518852)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Gallai–Hasse–Roy–Vitaver_theorem)  
**Source**: https://4ort.xyz/entity/gallai-hasse-roy-vitaver-theorem