@book { KreditkartengeschftStatusQuoundPotenzial,
    title = "Kreditkartengeschäft: Status Quo und Potenzial",
    author = "Susann {Lehniger}",
    year = "2005",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832489069",
    url = "https://m.diplom.de/document/224081"
}