| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] over a period of several | 7 |
|
| 2 | over a period of several [noun pl] | 15 |
|
| 3 | over a period of several [noun] | 15 |
|
| 4 | over a period of several year | 7 |
|
| 5 | over a period of several years | 7 |
|
