SN4 ""

No	Pattern	Freq
1	over a [adj] period [prep]	166
2	over a [adj] period [prep]	166
3	over a [adj] period of	128
4	over a [adj] period of	128
5	over a [adj] period [conj]	22
6	over a [adj] period [verb]	22
7	over a [adj] period [coord]	20
8	over a [adj] period and	18
9	over a [adj] period and	18
10	over a [adj] period [be]	9
11	over a [adj] period be	9
12	over a [adj] period [modal v]	7
13	over a [adj] period [vb mod]	7
14	over a [adj] period [v-ing]	7
15	over a [adj] period [adv]	6
16	over a [adj] period [is]	6
17	over a [adj] period in	6
18	over a [adj] period is	6
19	over a [adj] period in	6
20	over a [adj] period to	5
21	over a [adj] period [vb -s]	5
22	over a [adj] period from	5
23	over a [adj] period [to-vb]	5
24	over a [adj] period to	5
25	over a [adj] period from	5
26	[noun] over a [adj] period	262
27	[noun sg] over a [adj] period	156
28	[noun pl] over a [adj] period	87
29	[verb] over a [adj] period	73
30	[vb pp] over a [adj] period	71