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.
, and 
.
(a)(b) scale-free network against simultaneous and sequential attacks, respectively; (c)(d) exponential network against simultaneous and sequential attacks, respectively.
