@book { DerHrbuchmarktinDeutschland,
    title = "Der Hörbuchmarkt in Deutschland",
    author = "Ute {Hennig}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832444488",
    url = "https://m.diplom.de/document/220055"
}