| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] a long period [prep] | 13 |
|
| 2 | [adv] a long period of | 12 |
|
| 3 | over a long period [prep] | 9 |
|
| 4 | [adv prt] a long period [prep] | 9 |
|
| 5 | over a long period [prep] | 9 |
|
