Folding = Colouring

Abstract

The foldings of a connected graph $G$ are defined as follows. First, $G$ is a folding of itself. Let $G^{\prime }$ be a graph obtained from $G$ by identifying two vertices at distance 2 in $G$. Then every folding of $G^{\prime }$ is a folding of $G$. The folding number of $G$ is the minimum order of a complete folding of $G$. Theorem: The folding number of every graph equals its chromatic number.

I have discovered that the main result was first proved by Cook and Evans in 1979