Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Germ\'an Ancochea's work on projectivities, harmonicity preservers and
  semi-homomorphisms   Our main aim is to analyse three articles of Germ\'an Ancochea (published
1941, 1942 and 1947) and to describe their impact in algebra and geometry.

33
The categories of this paper are: plasm-ph
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
6
The categories of this paper are: astro-ph
16
The categories of this paper are: stat
34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
19
The categories of this paper are: eess
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio