SN4 ""

No	Pattern	Freq
1	over a [adj] period [prep]	176
2	over a [adj] period [prep]	166
3	over a long period [prep]	93
4	over a long period [prep]	85
5	over a [adj -er] period [prep]	10
6	over a short period [prep]	9
7	over a prolonged period [prep]	9
8	over a prolonged period [prep]	9
9	over a short period [prep]	8
10	over a longer period [prep]	8
11	over a considerable period [prep]	7
12	over a considerable period [prep]	7
13	over a given period [prep]	6
14	over a [noun] period [prep]	6
15	over a [noun sg] period [prep]	6
16	over a given period [prep]	6
17	[noun] over a period [prep]	295
18	[noun sg] over a period [prep]	168
19	[noun pl] over a period [prep]	105
20	[verb] over a period [prep]	76
21	[vb pp] over a period [prep]	71
22	[adv] over a period [prep]	60
23	[adv] over a period [prep]	34
24	[adj] over a period [prep]	28
25	[conj] over a period [prep]	25
26	[adv prt] over a period [prep]	25
27	[adj] over a period [prep]	19
28	[coord] over a period [prep]	18
29	[noun prp] over a period [prep]	12
30	and over a period [prep]	12