@book { DasZeichenamHutimMittelalter,
    title = "Das Zeichen am Hut im Mittelalter",
    author = "Hartmut {Kühne} and Lothar {Lambacher} and Konrad {Vanja}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1105022"
}