@book { DerHrbuchmarktimdeutschsprachigenRaum,
    title = "Der Hörbuchmarkt im deutschsprachigen Raum",
    subtitle = "Zum aktuellen Boom des Audiobooks",
    author = "Gerlinde {Freis}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832495725",
    url = "https://m.diplom.de/document/224481"
}