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.
An illustration of the construction of the CGR. In this example, given the sequence bbca, the following steps are taken: From centre to vertex b, mark midpoint 1 (arrowhead, address b); from 1 to b, mark midpoint 2 (address bb); from 2 to c, mark midpoint 3 (address bbc); from 3 to a, mark midpoint 4 (address bbca)
