| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [modal v] have been [verb] [prep] years | 6 |
|
| 2 | [vb mod] [verb] been [verb] [prep] years | 6 |
|
| 3 | [modal v] have been [verb] [prep] years | 6 |
|
| 4 | [modal v] [vb infin] been [verb] [prep] years | 6 |
|
