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Characters of the top 10 most productive countries/regions.
| Rank | Country | Documentsa | Citations |
|---|---|---|---|
| 1 | USA | 3392 | 160,697 |
| 2 | China | 1178 | 22,360 |
| 3 | UK | 477 | 24,042 |
| 4 | Italy | 341 | 8461 |
| 5 | Australia | 335 | 12,494 |
| 6 | Canada | 302 | 9300 |
| 7 | Germany | 297 | 9578 |
| 8 | Spain | 289 | 6593 |
| 9 | Sweden | 253 | 9011 |
| 10 | Netherlands | 250 | 9811 |
By corresponding author
