| No | Pattern | Freq | Relations |
|---|---|---|---|
| 1 | be [prep] [num] year ['s] duration | 51 |
|
| 2 | [be] [prep] [num] year ['s] duration | 51 |
|
| 3 | [be] of [num] year ['s] duration | 50 |
|
| 4 | [be] [prep] [num] year ' duration | 49 |
|
| 5 | [be] [prep] [num] years ['s] duration | 49 |
|
| 6 | is [prep] [num] year ['s] duration | 46 |
|
| 7 | [is] [prep] [num] year ['s] duration | 46 |
|
| 8 | [be] [prep] three year ['s] duration | 24 |
|
| 9 | [be] [prep] four year ['s] duration | 18 |
|
| 10 | [be] [prep] two year ['s] duration | 7 |
|
