I keep reading that Kempe has proven that every vertex in a 5-chroma planar graph must have degree >= 5, but nowhere can I find this proof.
Could someone please explain the proof or point me in the right direction?
Many thanks in advance,
Katie
I keep reading that Kempe has proven that every vertex in a 5-chroma planar graph must have degree >= 5, but nowhere can I find this proof.
Could someone please explain the proof or point me in the right direction?
Many thanks in advance,
Katie