| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] difficult [noun] [prep] | 347 |
|
| 2 | [adv] [adj] period [prep] | 250 |
|
| 3 | [adv] difficult [noun sg] [prep] | 239 |
|
| 4 | [adv] difficult period [prep] | 7 |
|
