@book { BeschwerdemanagementalsInstrumentderCustomerIntegration,
    title = "Beschwerdemanagement als Instrument der Customer Integration",
    author = "Markus {Kehren}",
    year = "1999",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832418373",
    url = "https://m.diplom.de/document/217689"
}