Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Survey on preopen sets   The aim of this survey article is to cover most of the recent research on
preopen sets. I try to present majority of the results on preopen sets that I
am aware of.

28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
21
The categories of this paper are: adap-org
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
27
The categories of this paper are: comp-gas
18
The categories of this paper are: econ
4
The categories of this paper are: cond-mat
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
9
The categories of this paper are: nlin