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.
(left) Even-size natural graph completed by adding two pairs of gray edges. (right) Two odd-size natural graphs, containing x,y,z vertices and a,b,c vertices, respectively, combined into one supernatural graph so that three pairs of gray edges may be added.
