Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photon Structure and gamma-gamma Physics   The LEP experiments are making real progress in understanding the structure
of the photon, though the results do not yet give such clear demonstrations of
QCD in action as the proton structure has done. Other new results are reported,
including QED related effects and $\gamma \gamma \to Resonances$, from LEP and
from CLEO II.

24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas