| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [art] [adv] difficult period | 12 |
|
| 2 | [art] [adv] difficult period | 12 |
|
| 3 | a [adv] difficult period | 9 |
|
| 4 | a [adv] difficult period | 8 |
|
| 5 | [adv] difficult period [prep] | 5 |
|
| 6 | [adv] difficult period [prep] | 5 |
|
