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.
Collaboration networks between countries (defined as more than one collaboration). The size of the nodes is proportional to the number of articles published by each country. Germany followed by the USA are the central countries in the network
