| Cg1 and Cg2 are the centroids of the N1/C1–C5 and N4/C9–C15 rings, respectively. |
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.