SN4 ""

No	Pattern	Freq
1	is [adv] difficult [to-vb]	825
2	is very difficult [to-vb]	228
3	is very difficult [to-vb]	228
4	is [not/n't] difficult [to-vb]	164
5	is not difficult [to-vb]	164
6	is not difficult [to-vb]	154
7	is more difficult [to-vb]	113
8	is more difficult [to-vb]	113
9	is extremely difficult [to-vb]	91
10	is extremely difficult [to-vb]	91
11	is often difficult [to-vb]	80
12	is often difficult [to-vb]	80
13	is [adv] difficult to see	59
14	is [adv] difficult to find	43
15	is [adv] difficult to make	30
16	is notoriously difficult [to-vb]	27
17	is notoriously difficult [to-vb]	27
18	is sometimes difficult [to-vb]	26
19	is sometimes difficult [to-vb]	26
20	is [adv] difficult to assess	25
21	is [adv] difficult to understand	25
22	is [adv] difficult to imagine	22
23	is always difficult [to-vb]	22
24	is always difficult [to-vb]	22
25	is [adv] difficult to determine	21
26	is [adv] difficult to establish	21
27	is [adv] difficult to predict	21
28	is [adv] difficult to get	21
29	is so difficult [to-vb]	20
30	is [adv] difficult to achieve	20