Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: X-ray observations of Clusters of Galaxies   X-ray observations of clusters provide key information on the dark matter, on
the formation of structures in the Universe, and can be used to constrain the
cosmological parameters. I review our current knowledge, with emphasis on
recent XMM and Chandra results.

18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
17
The categories of this paper are: q-fin
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
19
The categories of this paper are: eess
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
14
The categories of this paper are: math-ph