@book { WerbeerfolgsmessungimEBusiness,
    title = "Werbeerfolgsmessung im E-Business",
    author = "Edeltraud {Richtsfeld}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832464561",
    url = "https://m.diplom.de/document/221878"
}