SN4 ""

No	Pattern	Freq
1	[modal v] [adv] have [been] [adv]	555
2	[vb mod] [adv] have [been] [adv]	555
3	could [adv] have [been] [adv]	194
4	could [adv] have [been] [adv]	194
5	would [adv] have [been] [adv]	133
6	would [adv] have [been] [adv]	133
7	may [adv] have [been] [adv]	78
8	may [adv] have [been] [adv]	78
9	[noun] [adv] have [been] [adv]	50
10	might [adv] have [been] [adv]	49
11	might [adv] have [been] [adv]	49
12	[adv] [adv] have [been] [adv]	48
13	[verb] [adv] have [been] [adv]	43
14	can [adv] have [been] [adv]	35
15	[pron] [adv] have [been] [adv]	33
16	should [adv] have [been] [adv]	33
17	should [adv] have [been] [adv]	33
18	[noun sg] [adv] have [been] [adv]	30
19	[adv] [adv] have [been] [adv]	27
20	[conj] [adv] have [been] [adv]	23
21	[prep] [adv] have [been] [adv]	22
22	[prep] [adv] have [been] [adv]	22
23	can [adv] have [been] [adv]	21
24	[coord] [adv] have [been] [adv]	18
25	not [adv] have [been] [adv]	17
26	[not/n't] [adv] have [been] [adv]	17
27	[pers pn] [adv] have [been] [adv]	16
28	must [adv] have [been] [adv]	16
29	must [adv] have [been] [adv]	16
30	ca [adv] have [been] [adv]	14