| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | difficult [prep] [be] sure that | 5 |
|
| 2 | difficult to [be] sure [that] | 5 |
|
| 3 | difficult [prep] [be] sure [that] | 5 |
|
| 4 | difficult [prep] be sure [that] | 5 |
|
| 5 | difficult [prep] be sure [that] | 5 |
|
