SN4 ""

No	Pattern	Freq
1	over a [adj] period [prep] [noun]	134
2	over a [adj] period [prep] [noun sg]	129
3	over a [adj] period of [noun]	126
4	over a [adj] period [prep] time	120
5	over a [adj] period [prep] time	120
6	over a long period [prep] [noun]	84
7	over a long period [prep] [noun]	78
8	over a short period [prep] [noun]	8
9	over a considerable period [prep] [noun]	7
10	over a prolonged period [prep] [noun]	7
11	over a short period [prep] [noun]	7
12	over a prolonged period [prep] [noun]	7
13	over a [adj -er] period [prep] [noun]	7
14	over a considerable period [prep] [noun]	7
15	over a [adj] period [prep] [noun prp]	6
16	over a given period [prep] [noun]	6
17	over a longer period [prep] [noun]	6
18	over a given period [prep] [noun]	6
19	over a [adj] period [prep] years	5
20	over a [adj] period [prep] [noun pl]	5
21	over a [adj] period [prep] year	5