| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | difficult [to-vb] how | 314 |
|
| 2 | difficult to see how | 152 |
|
| 3 | difficult to know how | 34 |
|
| 4 | difficult to understand how | 26 |
|
| 5 | difficult to imagine how | 18 |
|
| 6 | difficult to say how | 12 |
|
| 7 | difficult to explain how | 9 |
|
| 8 | difficult to judge how | 7 |
|
| 9 | difficult to tell how | 6 |
|
| 10 | difficult to predict how | 5 |
|
| 11 | difficult to decide how | 5 |
|
| 12 | difficult to envisage how | 5 |
|
