@book { ECommercefrkleineundmittlereHandelsbetriebe,
    title = "E-Commerce für kleine und mittlere Handelsbetriebe",
    author = "Christian K. {Rupp}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836636803",
    url = "https://m.diplom.de/document/227259"
}