@book { DerStartindiePortrtfotografie,
    title = "Der Start in die Porträtfotografie",
    author = "Dirk {Schiff}",
    year = "2019",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/451593"
}