| An Empirical Study on Learning to Rank of Tweets Recent countries visiting this post |  |
 | 4 | United States |
 | 3 | China |
 | 1 | |
 | 1 | Russian Federation |
| An Empirical Study on Learning to Rank of Tweets Recent countries visiting this post | |
| 4 | United States |
| 3 | China |
| 1 | |
| 1 | Russian Federation |