Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Up to a double cover, every regular connected graph is isomorphic to a
  Schreier graph   We prove that every connected locally finite regular graph has a double cover
which is isomorphic to a Schreier graph.

13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
6
The categories of this paper are: astro-ph
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
11
The categories of this paper are: hep-lat
36
The categories of this paper are: cmp-lg
19
The categories of this paper are: eess
9
The categories of this paper are: nlin
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
16
The categories of this paper are: stat