SN4 ""

No	Pattern	Freq
1	over a [adv] [adj] period	19
2	over a [adv] [adj] period	19
3	over a [adj] [adj] period	10
4	over a [num] [adj] period	6
5	over a very [adj] period	6
6	over a very [adj] period	6
7	over a relatively [adj] period	5
8	over a relatively [adj] period	5
9	[noun] over a [adj] period	262
10	[noun sg] over a [adj] period	156
11	[noun pl] over a [adj] period	87
12	[verb] over a [adj] period	73
13	[vb pp] over a [adj] period	71
14	[adv] over a [adj] period	39
15	[adv] over a [adj] period	26
16	[adj] over a [adj] period	25
17	[conj] over a [adj] period	15
18	[adv prt] over a [adj] period	13
19	[adj] over a [adj] period	12
20	[coord] over a [adj] period	10
21	[n mass] over a [adj] period	10
22	[noun prp] over a [adj] period	9
23	[num] over a [adj] period	9
24	million over a [adj] period	6
25	million over a [adj] period	6
26	in over a [adj] period	5
27	in over a [adj] period	5
28	or over a [adj] period	5
29	[unc] over a [adj] period	5
30	that over a [adj] period	5