Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hadron structure after 25 years of QCD   We briefly review the status of our understanding of hadron structure based
on QCD. This includes the role of symmetries, especially chiral symmetry, and
the insights provided by lattice QCD. The main focus is on baryon structure and
especially the nucleon, but this cannot be treated realistically without
reference to spectroscopy. Our aim is to highlight recent insights and
promising directions for future work.

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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci