| Metrics for Vague Spatial Objects Based on the Concept of Mass Recent countries visiting this post |  |
 | 6 | United States |
 | 4 | China |
 | 1 | |
 | 1 | Europe |
 | 1 | Germany |
| Metrics for Vague Spatial Objects Based on the Concept of Mass Recent countries visiting this post | |
| 6 | United States |
| 4 | China |
| 1 | |
| 1 | Europe |
| 1 | Germany |