| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have [been] difficult | 180 |
|
| 2 | [verb] been difficult | 180 |
|
| 3 | [vb infin] [been] difficult | 80 |
|
| 4 | have [been] difficult | 79 |
|
| 5 | [vb -s] [been] difficult | 54 |
|
| 6 | has [been] difficult | 40 |
|
| 7 | had [been] difficult | 30 |
|
| 8 | [vb past] [been] difficult | 30 |
|
| 9 | [vb base] [been] difficult | 16 |
|
| 10 | have [been] difficult | 15 |
|
| 11 | 's [been] difficult | 14 |
|
