SN4 ""

No	Pattern	Freq
1	[noun] [prep] twenty year	159
2	[noun sg] [prep] twenty year	122
3	[verb] [prep] twenty year	68
4	[adv] [prep] twenty year	44
5	[adj] [prep] twenty year	37
6	[adv] [prep] twenty year	33
7	[vb pp] [prep] twenty year	31
8	[noun pl] [prep] twenty year	25
9	[pron] [prep] twenty year	20
10	[pers pn] [prep] twenty year	15
11	[adj] [prep] twenty year	14
12	[num] [prep] twenty year	14
13	period [prep] twenty year	13
14	[v-ing] [prep] twenty year	13
15	[vb past] [prep] twenty year	13
16	period [prep] twenty year	13
17	[conj] [prep] twenty year	11
18	[noun prp] [prep] twenty year	10
19	fifteen [prep] twenty year	9
20	[adv prt] [prep] twenty year	9
21	fifteen [prep] twenty year	9
22	[det] [prep] twenty year	9
23	it [prep] twenty year	7
24	[be] [prep] twenty year	7
25	it [prep] twenty year	7
26	be [prep] twenty year	7
27	there [prep] twenty year	6
28	up [prep] twenty year	6
29	there [prep] twenty year	6
30	up [prep] twenty year	6