| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | but it [is] difficult [verb] [conj] | 9 |
|
| 2 | but it [is] difficult [verb] [conj] | 9 |
|
| 3 | but it [is] difficult [to-vb] [conj] | 9 |
|
| 4 | but it is difficult [verb] [conj] | 8 |
|
