| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb past] to [be] [verb] | 8538 |
|
| 2 | [vb past] to [be] [vb pp] | 6822 |
|
| 3 | [verb] to [be] introduced | 78 |
|
| 4 | [vb past] to [be] introduce | 25 |
|
| 5 | [vb past] [prep] [be] introduced | 24 |
|
| 6 | [vb past] [prep] [be] introduced | 24 |
|
| 7 | [vb past] to [be] introduced | 23 |
|
