Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extragalactic radio surveys in the pre-Square Kilometre Array era   The era of the Square Kilometre Array is almost upon us, and pathfinder
telescopes are already in operation. This brief review summarizes our current
knowledge of extragalactic radio sources, accumulated through six decades of
continuum surveys at the low-frequency end of the electromagnetic spectrum and
the extensive complementary observations at other wavelengths necessary to gain
this understanding. The relationships between radio survey data and surveys at
other wavelengths are discussed. Some of the outstanding questions are
identified and prospects over the next few years are outlined.

1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
3
The categories of this paper are: physics
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
2
The categories of this paper are: math
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat
34
The categories of this paper are: chem-ph
37
The categories of this paper are: supr-con
9
The categories of this paper are: nlin
26
The categories of this paper are: bayes-an