| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | but it [is] often difficult [verb] | 5 |
|
| 2 | but it [is] often difficult [verb] | 5 |
|
| 3 | but it [is] often difficult [to-vb] | 5 |
|
| 4 | but it [is] often difficult [verb] | 5 |
|
