@book { EinfhrungindasBrgerlicheRecht,
    title = "Einführung in das Bürgerliche Recht",
    author = "Eugen {Klunzinger}",
    year = "2019",
    publisher = "Vahlen",
    address = "München, Deutschland",
    url = "https://vahlen.openpublishing.com/document/1221320"
}