SN4 ""

No	Pattern	Freq
1	[verb] at once	1025
2	[vb past] [prep] once	448
3	[vb pp] [prep] once	202
4	[vb infin] [prep] once	147
5	[vb base] [prep] once	95
6	know [prep] once	92
7	[v-ing] [prep] once	88
8	[to-vb] [prep] once	79
9	knew [prep] once	68
10	see [prep] once	66
11	say [prep] once	62
12	go [prep] once	52
13	[vb -s] [prep] once	49
14	said [prep] once	44
15	[verb] for once	38
16	saw [prep] once	35
17	come [prep] once	34
18	answer [prep] once	26
19	serve [prep] once	24
20	talk [prep] once	24
21	go [prep] once	24
22	talking [prep] once	21
23	serve [prep] once	21
24	leave [prep] once	20
25	have [prep] once	18
26	do [prep] once	18
27	see [prep] once	18
28	reply [prep] once	15
29	stop [prep] once	15
30	[verb] to once	14