SN4 ""

No	Pattern	Freq
1	have [been] [adv] used for	10
2	have [been] [adv] used for	10
3	have [been] widely used for	6
4	have [been] widely used for	6
5	[noun] have [been] used for	82
6	[pron] have [been] used for	42
7	[noun sg] have [been] used for	38
8	[noun pl] have [been] used for	37
9	which have [been] used for	22
10	[Wh det] have [been] used for	22
11	which have [been] used for	22
12	[conj] have [been] used for	20
13	[pers pn] have [been] used for	19
14	[vb mod] have [been] used for	15
15	[modal v] have [been] used for	15
16	it have [been] used for	14
17	that have [been] used for	14
18	that have [been] used for	14
19	it have [been] used for	14
20	[that] have [been] used for	14
21	[verb] have [been] used for	9
22	[adv] have [been] used for	8
23	[adj] have [been] used for	8
24	[adv] have [been] used for	7
25	[vb pp] have [been] used for	6
26	could have [been] used for	6
27	could have [been] used for	6
28	[noun prp] have [been] used for	5
29	may have [been] used for	5
30	[coord] have [been] used for	5