| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | when [verb] at | 231 |
|
| 2 | [conj] operate at | 29 |
|
| 3 | when operate [prep] | 13 |
|
| 4 | when operate [prep] | 13 |
|
| 5 | when operate at | 5 |
|
