Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Proof of a Conjecture of Ohba   We prove a conjecture of Ohba which says that every graph $G$ on at most
$2\chi(G)+1$ vertices satisfies $\chi_\ell(G)=\chi(G)$.

31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
21
The categories of this paper are: adap-org
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
27
The categories of this paper are: comp-gas
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
16
The categories of this paper are: stat
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph