Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Black hole entropy   We review black hole entropy with special reference to euclidean quantum
gravity, the brick wall approach and loop quantum gravity.

29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
0
The categories of this paper are: hep-ph
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
25
The categories of this paper are: patt-sol