| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] when [art] | 265 |
|
| 2 | [prep] 1987 [art] | 159 |
|
| 3 | [prep] 1987 when | 49 |
|
| 4 | 1987 when [art] | 18 |
|
