| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [verb] [been] necessary for [noun] | 8 |
|
| 2 | have [been] necessary for [noun] | 8 |
|
| 3 | [been] necessary for [noun] [to-vb] | 5 |
|
| 4 | [been] necessary for [noun] [verb] | 5 |
|
