Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Spanning trees of the World Trade Web: real-world data and the gravity
  model of trade
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
36
The categories of this paper are: cmp-lg
25
The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org