| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | so it [is] difficult [to-vb] | 13 |
|
| 2 | so it [is] difficult [to-vb] | 13 |
|
| 3 | so it is difficult [to-vb] | 7 |
|
| 4 | so it 's difficult [to-vb] | 6 |
|
