@book { NeukundengewinnungundbindungimInternet,
    title = "Neukundengewinnung und -bindung im Internet",
    author = "Stefan {Mellmann}",
    year = "2008",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836620413",
    url = "https://m.diplom.de/document/226232"
}