SN4 ""

No	Pattern	Freq
1	[noun] over a [adj] period	262
2	[noun sg] over a [adj] period	156
3	[noun] over a long period	95
4	[noun pl] over a [adj] period	87
5	[noun] over a five-year period	13
6	[noun] over a prolonged period	12
7	[n mass] over a [adj] period	10
8	[noun prp] over a [adj] period	9
9	[noun] over a three-year period	9
10	[noun] over a two-year period	8
11	[noun] over a given period	7
12	[noun] over a four-year period	7
13	[noun] over a short period	7
14	[noun] over a 24-hour period	6
15	[noun] over a lengthy period	6
16	[noun] over a 10-year period	5
17	[noun] over a sustained period	5