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.
The friend degree of a user is defined as their number of friendship ties. The encounter degree of a user is defined as their number of encounters during all period of observation.
