@Book{Kepler1933,
author  = "Kepler, Johannes",
title   = "Die Keplerbriefe auf der Braunschweigischen Landesbibliothek in Wolfenbüttel",
year    = "1933",
address = "München",
series  = "Abhandlungen",
volume  = "N.F., 18",
url     = "https://publikationen.badw.de/de/006296938",
}