| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | a long period of [noun sg] | 164 |
|
| 2 | a long period [prep] [noun sg] | 154 |
|
| 3 | a long period [prep] time | 115 |
|
| 4 | a longer period [prep] [noun sg] | 18 |
|
