@book { ViralMarketingimEBusiness,
    title = "Viral Marketing im E-Business",
    author = "Jean-Manuel {Leonardi}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836612944",
    url = "https://m.diplom.de/document/225778"
}