| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a period [modal v] | 5 |
|
| 2 | [prep] a period [modal v] | 5 |
|
| 3 | a [adj] period [modal v] | 32 |
|
| 4 | a [adj] period [modal v] | 26 |
|
| 5 | a long period [modal v] | 10 |
|
| 6 | a [adj -er] period [modal v] | 6 |
|
| 7 | a longer period [modal v] | 5 |
|
| 8 | a long period [modal v] | 5 |
|
| 9 | a period [pron] [modal v] | 8 |
|
| 10 | a period which [modal v] | 7 |
|
| 11 | a period [Wh det] [modal v] | 7 |
|
| 12 | a period which [modal v] | 7 |
|
