SN4 ""

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