| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] for 18 months | 43 |
|
| 2 | [be] [verb] for months | 37 |
|
| 3 | [be] [verb] for 18 | 29 |
|
| 4 | [be] [verb] 18 months | 13 |
|
