| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [prep] a [noun] [noun] [Wh det] | 1246 |
|
| 2 | [prep] [art] [noun] system [Wh det] | 74 |
|
| 3 | [prep] a [noun] system [pron] | 46 |
|
