SN4 ""

No	Pattern	Freq
1	[modal v] not have been [adj]	402
2	[vb mod] not have been [adj]	402
3	would not have been [adj]	224
4	would not have been [adj]	224
5	[modal v] not have been able	79
6	[modal v] not have been possible	65
7	may not have been [adj]	59
8	may not have been [adj]	59
9	could not have been [adj]	34
10	might not have been [adj]	34
11	might not have been [adj]	34
12	could not have been [adj]	34
13	can not have been [adj]	28
14	can not have been [adj]	28
15	[modal v] not have been easy	14
16	[modal v] not have been available	12
17	should not have been [adj]	11
18	should not have been [adj]	11
19	[modal v] not have been surprised	9
20	[modal v] not have been aware	8
21	[modal v] not have been necessary	8
22	need not have been [adj]	6
23	need not have been [adj]	6
24	[modal v] not have been sufficient	5
25	will not have been [adj]	5
26	[modal v] not have been popular	5
27	will not have been [adj]	5