Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Gauge covariance and the fermion-photon vertex in three- and four-
  dimensional, massless quantum electrodynamics
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
8
The categories of this paper are: hep-ex
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
29
The categories of this paper are: funct-an