Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Toroidal Obscuration of Active Galactic Nuclei   Observations give strong support for the unification scheme of active
galactic nuclei. The scheme is premised on toroidal obscuration of the central
engine by dusty clouds that are individually very optically thick. These
lectures summarize the torus properties, describe the handling and implications
of its clumpy nature and present speculations about its dynamic origin.

18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
14
The categories of this paper are: math-ph
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
31
The categories of this paper are: ao-sci