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.
(Left) We plot the total yearly ridership 
as a function of 
. A linear fit on the 
data points gives 
(
) which leads to a typical effective length of attraction 
per station. (Right) Map of Paris (France) with each subway station represented by a red circle of radius 
.
