| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | investigated at the time [prep] | 5 |
|
| 2 | investigate at the time [prep] | 5 |
|
| 3 | investigate at the time of | 5 |
|
| 4 | investigate at the time [prep] | 5 |
|
| 5 | investigate at the time of | 5 |
|
