| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | was introduced [prep] the [num ord] | 13 |
|
| 2 | [was/were] introduced in the [num ord] | 11 |
|
| 3 | were introduced [prep] the [num ord] | 8 |
|
| 4 | [was/were] introduced [prep] the first | 7 |
|
