SN4 ""

No	Pattern	Freq
1	at [adj] period [prep]	63
2	at [det] period [prep]	34
3	at [adj] period [prep]	26
4	at this period [prep]	15
5	at this period [prep]	15
6	at [art] period [prep]	13
7	at [art] period [prep]	13
8	at different period [prep]	11
9	at different period [prep]	11
10	at that period [prep]	7
11	at any period [prep]	7
12	at that period [prep]	7
13	at a period [prep]	7
14	at a period [prep]	7
15	at any period [prep]	7
16	at the period [prep]	6
17	at the period [prep]	6
18	at period [prep] [noun]	5
19	at period [prep] [noun sg]	5