SN4 ""

No	Pattern	Freq
1	which have been [verb] [prep]	2749
2	which have been [vb pp] [prep]	2621
3	which had been [verb] [prep]	1315
4	which has been [verb] [prep]	833
5	which have been [verb] by	711
6	which have been [verb] [prep]	600
7	which have been [verb] in	548
8	which have been [verb] to	289
9	which have been [verb] for	215
10	which have been [v-ing] [prep]	128
11	which have been [verb] on	128
12	which have been [verb] from	125
13	which have been [verb] with	123
14	which have been [verb] as	110
15	which have been [verb] at	86
16	which have been [verb] into	79
17	which have been use [prep]	61
18	which have been used [prep]	61
19	which have been made [prep]	59
20	which have been make [prep]	59
21	which have been develop [prep]	56
22	which have been developed [prep]	53
23	which have been [verb] since	42
24	which have been [verb] over	40
25	which have been establish [prep]	35
26	which have been established [prep]	35
27	which have been described [prep]	31
28	which have been describe [prep]	31
29	which have been built [prep]	30
30	which have been build [prep]	30