@book { KundenbewertunginB2BUnternehmen,
    title = "Kundenbewertung in B2B Unternehmen",
    author = "Matthias {Kupka}",
    year = "2021",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    url = "https://m.diplom.de/document/983474"
}