@Book{Hilbert1905,
author  = "Hilbert, Carl S.",
title   = "Über das Prinzip der kleinsten Wirkung",
year    = "1905",
address = "München",
series  = "Sitzungsberichte",
volume  = "1904,9",
url     = "https://publikationen.badw.de/en/003395039",
}