| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | difficult to [be] [adj] | 88 |
|
| 2 | difficult to be [adj] | 88 |
|
| 3 | difficult to [be] sure | 30 |
|
| 4 | difficult to [be] certain | 15 |
|
| 5 | difficult to [be] precise | 7 |
|
