| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is difficult [to-vb] | 1523 |
|
| 2 | is difficult [to-vb] [art] | 334 |
|
| 3 | it is [to-vb] [art] | 271 |
|
| 4 | it difficult [to-vb] [art] | 229 |
|
