SN4 ""

No	Pattern	Freq
1	[prep] once [noun]	112
2	[prep] once [noun]	112
3	[conj] once [noun]	106
4	[noun] once [noun]	96
5	be once [noun]	92
6	[be] once [noun]	92
7	[was/were] once [noun]	91
8	[coord] once [noun]	83
9	at once [noun]	69
10	at once [noun]	69
11	[verb] once [noun]	59
12	[noun sg] once [noun]	59
13	was once [noun]	59
14	but once [noun]	49
15	but once [noun]	49
16	for once [noun]	38
17	for once [noun]	38
18	[adv] once [noun]	35
19	and once [noun]	34
20	and once [noun]	34
21	were once [noun]	32
22	[adv] once [noun]	30
23	[vb pp] once [noun]	24
24	[noun pl] once [noun]	23
25	[subord] once [noun]	22
26	[noun prp] once [noun]	13
27	[adj] once [noun]	10
28	where once [noun]	10
29	where once [noun]	10
30	[vb infin] once [noun]	10