| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | at least three years ['s] | 5 |
|
| 2 | at least three years ['s] | 5 |
|
| 3 | [prep] least three years ['s] | 5 |
|
| 4 | [prep] least three years ' | 5 |
|
