SN4 ""

No	Pattern	Freq
1	[adv] difficult [to-vb]	3329
2	very difficult [to-vb]	892
3	more difficult [to-vb]	810
4	extremely difficult [to-vb]	233
5	[adv] difficult to get	155
6	often difficult [to-vb]	136
7	increasingly difficult [to-vb]	130
8	so difficult [to-vb]	128
9	too difficult [to-vb]	114
10	[adv] difficult to find	108
11	quite difficult [to-vb]	97
12	[adv] difficult to achieve	83
13	most difficult [to-vb]	77
14	[adv] difficult to make	71
15	[adv] difficult to do	70
16	[adv] difficult to see	68
17	[adv] difficult to understand	62
18	[adv] difficult to assess	59
19	notoriously difficult [to-vb]	57
20	rather difficult [to-vb]	53
21	[adv] difficult to keep	47
22	sometimes difficult [to-vb]	44
23	particularly difficult [to-vb]	44
24	[adv] difficult to explain	44
25	[adv] difficult to say	42
26	[adv] difficult to determine	40
27	[adv] difficult to obtain	40
28	[adv] difficult to distinguish	40
29	always difficult [to-vb]	37
30	[adv] difficult to establish	36