| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [to-vb] at [art] | 3827 |
|
| 2 | difficult [to-vb] [art] | 1328 |
|
| 3 | difficult [to-vb] at | 75 |
|
| 4 | difficult at [art] | 14 |
|
