@book { DerPrinzundderSchlssel,
    title = "Der Prinz und der Schlüssel",
    author = "David J. {Greening}",
    year = "2020",
    publisher = "Schreibstark-Verlag",
    address = ", Deutschland",
    url = "https://tolino.openpublishing.com/document/1014889"
}