Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: On The Structure of Dyck Languages   We prove that the closure of the one-sided Dyck language in a free monoid is
a two-sided Dyck language.

9
The categories of this paper are: nlin
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
22
The categories of this paper are: chao-dyn
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th