Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observatories   I give a brief history of astronomical observatories as an institution. This
includes: 1) observatories in Islam; 2) China and India; 3) early European
observatories; 4) the rise of national observatories; 5) private (amateur)
observatories; 6) mountaintop observatories and the modern era. Additional
references, to material not cited in the version that will be published in the
encyclopedia, are also given.

33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
29
The categories of this paper are: funct-an
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
21
The categories of this paper are: adap-org
31
The categories of this paper are: ao-sci
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
2
The categories of this paper are: math
20
The categories of this paper are: acc-phys
36
The categories of this paper are: cmp-lg