SN4 ""

No	Pattern	Freq
1	[noun sg] at period	5
2	[noun] at period	5
3	at [adj] period	269
4	at [det] period	193
5	at this period	123
6	at this period	123
7	at [adj] period	61
8	at that period	40
9	at that period	40
10	at [art] period	36
11	at [art] period	36
12	at a period	17
13	at a period	17
14	at different period	16
15	at the period	16
16	at the period	16
17	at different period	16
18	at any period	14
19	at any period	14
20	at certain period	11
21	at [noun sg] period	11
22	at certain period	11
23	at [noun] period	11
24	at [num] period	10
25	at one period	10
26	at one period	10
27	at all period	8
28	at all period	8
29	at other period	7
30	at peak period	7