@book { MarketingResearchOnline,
    title = "Marketing - Research Online",
    subtitle = "Möglichkeiten und Grenzen",
    author = "Anja {Krutzke} and Ute {Krogbäumker}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832452124",
    url = "https://m.diplom.de/document/220739"
}