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.
World distribution of selected studies (This map was generated from raw material in the website http://www.1ppt.com/article/2921.html. Microsoft Office Excel & Powerpoint Professional Plus 2007(Microsoft Corporation, Redmond, WA) were used to modify the picture.
