| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | it is difficult [verb] for | 13 |
|
| 2 | it is [adj] account for | 10 |
|
| 3 | it is [adj] account for | 9 |
|
| 4 | it [is] difficult account for | 6 |
|
| 5 | [pers pn] is difficult account for | 6 |
|
| 6 | it is difficult account for | 6 |
|
| 7 | it is difficult account for | 6 |
|
| 8 | [pron] is difficult account for | 6 |
|
| 9 | it [be] difficult account for | 6 |
|
| 10 | it is difficult account [prep] | 6 |
|
| 11 | it be difficult account for | 6 |
|
