| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv prt] a [adj] period of | 19 |
|
| 2 | over a [adj] period of | 16 |
|
| 3 | [adv prt] a long period of | 8 |
|
| 4 | [adv prt] a long period of | 8 |
|
