SN4 ""

No	Pattern	Freq
31	[noun sg] over a [adj] period	156
32	[noun sg] over a long period	81
33	[noun sg] over a long period	66
34	[noun sg] over a [adj -er] period	16
35	[noun sg] over a longer period	15
36	[noun sg] over a four-year period	7
37	[noun sg] over a four-year period	7
38	[noun sg] over a five-year period	6
39	[noun sg] over a five-year period	6
40	[noun sg] over a prolonged period	6
41	[noun sg] over a prolonged period	6
42	[noun sg] over a short period	5
43	[noun sg] over a lengthy period	5
44	[noun sg] over a three-year period	5
45	[noun sg] over a short period	5
46	[noun sg] over a [noun sg] period	5
47	[noun sg] over a three-year period	5
48	[noun sg] over a [noun] period	5
49	[noun sg] over a lengthy period	5
50	[noun sg] over a period [prep]	168
51	[noun sg] over a period [prep]	168
52	[noun sg] over a period of	165
53	[noun sg] over a period of	165