@book { DreiDateszuWeihnachten,
    title = "Drei Dates zu Weihnachten",
    author = "J. {Gerhardt}",
    year = "2021",
    publisher = "dp DIGITAL PUBLISHERS GmbH",
    address = "Stuttgart, Deutschland",
    url = "https://shop.digitalpublishers.de/document/1146200"
}