| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a long period [conj] | 13 |
|
| 2 | [prep] a long period [conj] | 13 |
|
| 3 | over a long period [conj] | 10 |
|
| 4 | over a long period [conj] | 10 |
|
| 5 | a long period [conj] [pron] | 6 |
|
