Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modified dispersionless Veselov--Novikov equations and corresponding
  hydrodynamic chains   Various links connecting well-known hydrodynamic chains and corresponding 2+1
nonlinear equations are described.

25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
13
The categories of this paper are: quant-ph