@book { DasInternetalsMarketingmedium,
    title = "Das Internet als Marketingmedium",
    author = "Carsten {Müller}",
    year = "1998",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832407148",
    url = "https://m.diplom.de/document/216233"
}