| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [noun] [verb] been [prep] operation since | 5 |
|
| 2 | [noun] [verb] been in operation since | 5 |
|
| 3 | [noun] have been [prep] operation since | 5 |
|
| 4 | [noun sg] [verb] been [prep] operation since | 5 |
|
