SN4 ""

No	Pattern	Freq
1	[adv] once a [noun]	332
2	[noun] once a [noun]	298
3	[adv] once a [noun]	294
4	[noun sg] once a [noun]	206
5	[verb] once a [noun]	190
6	[be] once a [noun]	132
7	be once a [noun]	132
8	[was/were] once a [noun]	119
9	least once a [noun]	117
10	least once a [noun]	117
11	[conj] once a [noun]	116
12	was once a [noun]	109
13	[pron] once a [noun]	63
14	[noun pl] once a [noun]	62
15	[vb pp] once a [noun]	59
16	[prep] once a [noun]	56
17	[prep] once a [noun]	56
18	[pers pn] once a [noun]	54
19	only once a [noun]	51
20	[coord] once a [noun]	51
21	only once a [noun]	51
22	[subord] once a [noun]	46
23	about once a [noun]	39
24	about once a [noun]	39
25	[vb base] once a [noun]	36
26	[adv prt] once a [noun]	34
27	than once a [noun]	31
28	than once a [noun]	31
29	at once a [noun]	29
30	at once a [noun]	29