@book { FlexibilityMeasurementwithintheServiceindustry,
    title = "Flexibility Measurement within the Service industry",
    author = "Tobias {Kunze}",
    year = "2009",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783836625395",
    url = "https://m.diplom.de/document/226509"
}