No | Pattern | Freq | Relations |
---|---|---|---|
1 | [vb past] over a period of | 19 | |
2 | [v-ing] over a period of | 12 | |
3 | [vb -s] over a period of | 8 | |
4 | [to-vb] over a period of | 6 | |
5 | [vb base] over a period of | 6 | |
6 | occur over a period of | 5 | |
7 | extend over a period of | 5 | |
8 | [vb infin] over a period of | 5 |