A Markoff triple $(a,b,c)$ is a solution in positive integers to the equation $$ a^2+b^2+c^2=3abc. $$ Frobenius famously conjectured that a given integer $c$ may appear at most once as the largest coordinate of a Markoff triple $(a,b,c)$, a conjecture often referred to as the Unicity Conjecture. This conjecture appears (I've been told) in the paper
G. Frobenius, Über die Markoffschen Zahlen, S. B. Preuss Akad. Wiss., Berlin, 1913, pp. 458–487.
I was wondering if anyone knows where to find a copy of this paper on the web; or if you have a copy, would it be possible for you to send me a PDF? It's long out of copyright, so that shouldn't be an issue. I tried a general web search, and Google Scholar, but no success. [I'd be even more appreciative of a translation into English, since my German reading skills are rusty; but probably that's too much to hope for.]