@book { KundenbindunginderGastronomie,
    title = "Kundenbindung in der Gastronomie",
    author = "Jan {Dauge}",
    year = "2003",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832471361",
    url = "https://m.diplom.de/document/222449"
}