| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | [vb base] been [v-ing] for several years | 6 |
|
| 2 | [vb base] [been] [v-ing] for several years | 6 |
|
| 3 | [vb base] be [v-ing] for several years | 6 |
|
| 4 | [vb base] [be] [v-ing] for several years | 6 |
|
