SN4 ""

No	Pattern	Freq
1	[adv] once but	39
2	[not/n't] once but	22
3	not once but	22
4	not once but	22
5	[adv] once but	13
6	[prep] once but	12
7	[prep] once but	12
8	at once but	11
9	at once but	11
10	[pron] once but	8
11	[pers pn] once but	8
12	[noun] once but	6
13	[verb] once but	6
14	it once but	6
15	[noun sg] once but	6
16	it once but	6
17	just once but	5
18	there once but	5
19	there once but	5
20	just once but	5
21	once [adv] but	9
22	once [adv] but	9
23	once [verb] but	9
24	once [adj] but	7
25	once [adj] but	7
26	once [vb pp] but	5
27	once again but	5
28	once again but	5
29	once but [adv]	20
30	once but [adv]	17