| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be [prep] [num] years ' duration | 49 |
|
| 2 | be [prep] [num] years ' duration | 49 |
|
| 3 | be [prep] [num] years ' duration | 49 |
|
| 4 | be of [num] years ' duration | 48 |
|
| 5 | be of [num] years ' duration | 48 |
|
| 6 | is [prep] [num] years ' duration | 45 |
|
| 7 | be [prep] three years ' duration | 24 |
|
| 8 | be [prep] four years ' duration | 18 |
|
| 9 | be [prep] two years ' duration | 7 |
|
