@Book{Lettenmeyer1933,
author  = "Lettenmeyer, Fritz",
title   = "Gleichungen unendlich hohen Grades in zwei Variabeln",
year    = "1933",
address = "München",
series  = "Sitzungsberichte",
volume  = "1933,[20]",
url     = "https://publikationen.badw.de/de/003895876",
}