| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | been [vb pp] [prep] [art] period of | 21 |
|
| 2 | [been] [vb pp] [prep] [art] period of | 21 |
|
| 3 | [been] [vb pp] [prep] a period of | 19 |
|
| 4 | [been] [vb pp] by [art] period of | 6 |
|
| 5 | [been] [vb pp] in [art] period of | 5 |
|
