SN4 ""

No	Pattern	Freq
1	[noun] over a [adj] period	289
2	[noun] over a [adj] period	262
3	[noun sg] over a [adj] period	172
4	[noun] over a long period	120
5	[noun pl] over a [adj] period	98
6	[noun] over a long period	95
7	[noun] over a [adj -er] period	27
8	[noun] over a longer period	25
9	[noun] over a five-year period	13
10	[noun] over a five-year period	13
11	[noun] over a prolonged period	12
12	[noun] over a prolonged period	12
13	[n mass] over a [adj] period	10
14	[noun prp] over a [adj] period	9
15	[noun] over a three-year period	9
16	[noun] over a three-year period	9
17	[noun] over a two-year period	8
18	[noun] over a short period	8
19	[noun] over a two-year period	8
20	[noun] over a given period	7
21	[noun] over a four-year period	7
22	[noun] over a four-year period	7
23	[noun] over a given period	7
24	[noun] over a short period	7
25	[noun] over a 24-hour period	6
26	[noun] over a lengthy period	6
27	[noun] over a 24-hour period	6
28	[noun] over a lengthy period	6
29	[noun] over a sustained period	5
30	[noun] over a 10-year period	5