@book { ZahlungsverfahrenfrdasInternet,
    title = "Zahlungsverfahren für das Internet",
    author = "Thomas {Haim}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832451288",
    url = "https://m.diplom.de/document/220655"
}