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.
Countries with international collaborations exceeding fifteen.
| From | To | Frequency |
|---|---|---|
| USA | Canada | 40 |
| USA | Germany | 39 |
| Switzerland | Germany | 32 |
| USA | UK | 30 |
| USA | Switzerland | 27 |
| Belgium | Switzerland | 22 |
| USA | Belgium | 19 |
| United Kingdom | Switzerland | 18 |
| USA | Netherlands | 18 |
| Belgium | Germany | 17 |
| UK | Belgium | 16 |
| UK | Germany | 16 |
