SN4 ""

No	Pattern	Freq
1	it [adv] difficult [to-vb]	366
2	it very difficult [verb]	129
3	it more difficult [verb]	72
4	it increasingly difficult [verb]	49
5	it extremely difficult [verb]	31
6	it [adv] difficult get	29
7	it [adv] difficult to get	29
8	it so difficult [verb]	20
9	it [adv] difficult to understand	12
10	it [adv] difficult understand	12
11	it quite difficult [verb]	11
12	it [adv] difficult to make	9
13	it rather difficult [verb]	9
14	it [adv] difficult find	9
15	it [adv] difficult make	9
16	it [adv] difficult to find	8
17	it too difficult [verb]	7
18	it [adv] difficult work	7
19	it [adv] difficult to work	7
20	it [adv] difficult to keep	7
21	it particularly difficult [verb]	7
22	it [adv] difficult keep	7
23	it [adv] difficult obtain	6
24	it [adv] difficult to obtain	6
25	it [adv] difficult maintain	6
26	it [adv] difficult to maintain	6
27	it [adv] difficult to see	5
28	it [adv] difficult accept	5
29	it [adv] difficult do	5
30	it [adv] difficult to give	5