Search our collection of background (non-event) articles from news media, science journals and other sources.
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15 | ||
5 | ||
3 | ||
3 | ||
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9 | ||
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8 | ||
2 | ||
2 | ||
1 | ||
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7 | 8 |
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1 | 1 | 3 | 1 | 6 | 1 | 2 |
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United States | 9 | |
Canada | 2 | |
Norway | 2 | |
Russia | 1 |