Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Integrable KdV Systems: Recursion Operators of Degree Four   The recursion operator and bi-Hamiltonian formulation of the Drinfeld-
Sokolov system are given

16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas
17
The categories of this paper are: q-fin
7
The categories of this paper are: hep-th
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
21
The categories of this paper are: adap-org
11
The categories of this paper are: hep-lat
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con