SN4 ""

No	Pattern	Freq
1	when do	955
2	when [vb past]	606
3	when did	568
4	when [to-vb]	471
5	when [vb base]	379
6	when do	249
7	when [vb -s]	156
8	when [v-ing]	118
9	when does	106
10	when have	106
11	when [vb pp]	81
12	when stop	43
13	when to stop	40
14	when have	37
15	when had	37
16	when has	28
17	when go	27
18	when use	24
19	when to go	23
20	when to use	21
21	when leave	18
22	when to do	17
23	when to seek	15
24	when make	15
25	when seek	15
26	when to leave	14
27	when take	13
28	when get	12
29	when change	12
30	when to change	11