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.
, 2, 4, or 8 movies, respectively.
The solid line has a slope, the exponent of the power law degree distribution, 
(see text).
