SN4 ""

No	Pattern	Freq
1	[noun] over a long period	120
2	[noun sg] over a long period	81
3	[verb] over a long period	46
4	[vb pp] over a long period	44
5	[noun pl] over a long period	34
6	[adv] over a long period	22
7	[adv] over a long period	17
8	[conj] over a long period	11
9	[coord] over a long period	8
10	[adj] over a long period	6
11	[adv prt] over a long period	5
12	over [det] a long period	5
13	over such a long period	5
14	over such a long period	5
15	over [adj] a long period	5
16	over a [adv] long period	21
17	over a [adv] long period	21
18	over a much long period	9
19	over a much long period	9
20	over a long period [prep]	93
21	over a long period [prep]	93
22	over a long period of	84
23	over a long period of	84
24	over a long period [conj]	16
25	over a long period [coord]	12
26	over a long period and	11
27	over a long period and	11
28	over a long period [vb mod]	5
29	over a long period [modal v]	5
30	over a long period [verb]	5