Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Suggestions for Identifying the Primary of Post-GZK Air Showers   A procedure is suggested for systematically narrowing the choice of possible
primaries for (UHECR) air showers with energies beyond the
Greisen-Zatsepin-Kuz'min cut-off of $4 \times 10^{19} eV$.

37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
1
The categories of this paper are: cs
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin