@Book{Schur1927,
author  = "Schur, Friedrich",
title   = "Der Hauptsatz der Polarentheorie der Kegelschnitte",
year    = "1927",
address = "München",
series  = "Sitzungsberichte",
volume  = "1927,19",
url     = "https://publikationen.badw.de/en/003383213",
}