Figure 10.
Two unique 2-colourings, up to isomorphism, of quotient graphs of hcb by subgroups of index 2 (left) 
and 3 (right) 
.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.