SN4 ""

No	Pattern	Freq
31	[vb infin] [noun] over a period	5
32	their [noun] over a period	5
33	[noun] [noun] over a period	40
34	[noun] [noun pl] over a period	20
35	[noun] [noun sg] over a period	17
36	[noun] [adv] over a period	11
37	[noun] [verb] over a period	9
38	[noun] [vb pp] over a period	9
39	[noun] [adv] over a period	9
40	[noun] [conj] over a period	8
41	[noun] [coord] over a period	7
42	[noun] and over a period	5
43	[noun] and over a period	5
44	[noun] over a [adj] period	289
45	[noun] over a [adj] period	262
46	[noun] over a long period	120
47	[noun] over a long period	95
48	[noun] over a [adj -er] period	27
49	[noun] over a longer period	25
50	[noun] over a five-year period	13
51	[noun] over a five-year period	13
52	[noun] over a prolonged period	12
53	[noun] over a prolonged period	12
54	[noun] over a three-year period	9
55	[noun] over a three-year period	9
56	[noun] over a [noun] period	9
57	[noun] over a two-year period	8
58	[noun] over a [noun sg] period	8
59	[noun] over a short period	8
60	[noun] over a two-year period	8