| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a [adj -er] period [prep] | 63 |
|
| 2 | a [adj -er] period of | 54 |
|
| 3 | a [adj -er] period of | 54 |
|
| 4 | a longer period [prep] | 29 |
|
| 5 | a further period [prep] | 22 |
|
| 6 | a shorter period [prep] | 7 |
|
