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.
Distribution by country.
| Rank | Country | Documents, n (%) | Citations, n | Average citations | Total link strength |
| 1 | USA | 1454 (58.4) | 40337 | 27.7 | 549 |
| 2 | China | 414 (16.6) | 6537 | 15.8 | 206 |
| 3 | UK | 305 (12.3) | 9026 | 29.6 | 214 |
| 4 | Germany | 225 (9.0 ) | 5384 | 23.9 | 162 |
| 5 | Sweden | 134 (5.4) | 6973 | 52.0 | 88 |
| 6 | Japan | 108 (4.3) | 1454 | 13.5 | 68 |
| 7 | Switzerland | 104 (4.2) | 1802 | 17.3 | 72 |
| 8 | Australia | 99 (4.0) | 2442 | 24.7 | 70 |
| 9 | Canada | 85 (3.4) | 3177 | 37.4 | 53 |
| 10 | Netherlands | 85 (3.4) | 1330 | 15.7 | 67 |
