| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adj] [to-vb] [is] [not/n't] | 31 |
|
| 2 | difficult [to-vb] [is] [adv] | 13 |
|
| 3 | difficult [to-vb] [be] [not/n't] | 11 |
|
| 4 | difficult [verb] [is] [not/n't] | 11 |
|
