| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | can be [vb pp] back to | 84 |
|
| 2 | can be [verb] back to | 84 |
|
| 3 | can be [verb] back to | 84 |
|
| 4 | can be trace back to | 70 |
|
| 5 | can be traced back to | 70 |
|
