| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [conj] [v-ing] [prep] | 19874 |
|
| 2 | back [conj] [v-ing] | 160 |
|
| 3 | back [conj] [prep] | 77 |
|
| 4 | back [v-ing] [prep] | 49 |
|
