@Book{Beck1917,
author  = "Beck, Hans",
title   = "Die beiden Geraden-Kugeltransformationen von Sophus Lie",
year    = "1917",
address = "München",
series  = "Sitzungsberichte",
volume  = "1917,4",
url     = "https://publikationen.badw.de/de/003395555",
}