While perusing p. 237 of the 3rd ed. of Marvin Greenberg's book on Euclidean and non-Euclidean geometries, I learned that it can actually be proven that "*all possible models of hyperbolic geometry are isomorphic to one another,* i.e., that the axioms for hyperbolic geometry are *categorical*".

This assertion made me wonder if the analogous result for the axioms for elliptic geometry holds true. Unfortunately, I couldn't find a remark regarding this issue in Greenberg's book. I believe that an answer can be found in the following reference:

W. Schwabhäuser, On models of elementary elliptic geometry. Theory of Models (Proc. 1963 Internat. Sympos. Berkeley), pp. 312–328. North-Holland Publishing Co., Amsterdam, 1965.

Since this article is behind a paywall for me, I would like to know if anybody here has already read it and can tell me whether or not Schwabhäuser establishes the *categoricity* of some version of elliptic geometry therein... In case Schwabhäuser proves nothing of this sort in the said article, what would be the paper to look at in order to know the state of the art regarding the axioms for elliptic geometry?

Thanks in advance for taking the time to take a look at this question of mine.