SN4 ""

No	Pattern	Freq
1	at [det] levels	556
2	at all levels	474
3	at all levels	474
4	at [adj] levels	414
5	at [num] levels	132
6	at different levels	118
7	at different levels	118
8	at [adj -er] levels	102
9	at low levels	82
10	at high levels	64
11	at lower levels	51
12	at various levels	51
13	at various levels	51
14	at higher levels	41
15	at two levels	34
16	at two levels	34
17	at three levels	34
18	at three levels	34
19	at low levels	31
20	at 1990 levels	30
21	at 1990 levels	30
22	at high levels	23
23	at many levels	21
24	at many levels	21
25	at current levels	20
26	at current levels	20
27	at these levels	19
28	at these levels	19
29	at several levels	17
30	at several levels	17