| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | over the [num ord] 18 months | 29 |
|
| 2 | over [art] [num ord] 18 months | 29 |
|
| 3 | over [art] [num ord] 18 months | 29 |
|
| 4 | over [art] next 18 months | 18 |
|
| 5 | over [art] last 18 months | 11 |
|
