| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [adv] [be] [verb] back to | 29 |
|
| 2 | [adv] be [verb] back to | 29 |
|
| 3 | [adv] [be] [vb pp] back to | 23 |
|
| 4 | [adv] [be] trace back to | 9 |
|
| 5 | [adv] [be] traced back to | 9 |
|
| 6 | then [be] [verb] back to | 6 |
|
| 7 | [adv] [be] [v-ing] back to | 6 |
|
