Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: FIRST-2MASS Sources Below the APM Detection Threshold: A Population of
  Highly Reddened Quasars
7
The categories of this paper are: hep-th
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
11
The categories of this paper are: hep-lat
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
3
The categories of this paper are: physics
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
16
The categories of this paper are: stat
1
The categories of this paper are: cs