Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Urban Scaling in Europe
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
4
The categories of this paper are: cond-mat
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
21
The categories of this paper are: adap-org
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg