@book { CreditRatingimMittelstand,
    title = "Credit Rating im Mittelstand",
    author = "Miriam {Brockhaus}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832449674",
    url = "https://m.diplom.de/document/220533"
}