| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | difficult [to-vb] [conj] [prep] [art] | 29 |
|
| 2 | [am/are] difficult [to-vb] [prep] [art] | 23 |
|
| 3 | [am/are] difficult [to-vb] [conj] [prep] | 11 |
|
| 4 | [am/are] difficult [to-vb] [conj] [art] | 8 |
|
