SN4 ""

No	Pattern	Freq
1	over a [adj] [noun sg] period	142
2	over a [adj] [noun] period	142
3	over a [adj] year period	71
4	over a [adj] year period	71
5	over a [adj] month period	25
6	over a [adj] month period	25
7	over a [adj] day period	14
8	over a [adj] day period	14
9	over a [adj] week period	13
10	over a [adj] week period	13
11	over a [adj] [adj] period	10
12	over a [adj] [adj] period	10
13	over a [adj] hour period	8
14	over a [adj] hour period	8
15	over a [adj] time period	7
16	over a [adj] time period	7
17	over a [adj] minute period	6
18	over a [adj] minute period	6
19	[noun] over a [adj] period	289
20	[noun sg] over a [adj] period	172
21	[noun pl] over a [adj] period	98
22	[verb] over a [adj] period	86
23	[vb pp] over a [adj] period	83
24	[adv] over a [adj] period	43
25	[adv] over a [adj] period	29
26	[adj] over a [adj] period	27
27	[conj] over a [adj] period	17
28	[adv prt] over a [adj] period	14
29	[adj] over a [adj] period	13
30	[coord] over a [adj] period	11