@Book{Vogel1881,
author  = "Vogel, August",
title   = "Beitrag zur Kenntniss des Copal's",
year    = "1881",
address = "München",
series  = "Sitzungsberichte",
volume  = "1881,8",
url     = "https://publikationen.badw.de/en/003395071",
}