@book { PrinzTheoundderElfenbeinturm,
    title = "Prinz Theo und der Elfenbeinturm",
    author = "Volker {Friebel}",
    year = "2019",
    publisher = "Edition Blaue Felder, Tübingen",
    address = ", Deutschland",
    url = "https://tolino.openpublishing.com/document/998839"
}