| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | have [been] in operation [prep] [det] | 8 |
|
| 2 | have been in operation [prep] [det] | 8 |
|
| 3 | have [been] in operation for [det] | 7 |
|
| 4 | have [been] in operation [prep] some | 5 |
|
