| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv prt] a period of | 67 |
|
| 2 | over a period of | 61 |
|
| 3 | over a period of | 61 |
|
| 4 | [adv] a period of | 37 |
|
| 5 | long a period of | 6 |
|
| 6 | long a period of | 6 |
|
| 7 | not a period of | 5 |
|
| 8 | [not/n't] a period of | 5 |
|
| 9 | not a period of | 5 |
|
