@book { QualittsmanagementinDienstleistungsunternehmen,
    title = "Qualitätsmanagement in Dienstleistungsunternehmen",
    author = "Henning {Wallraff}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832443511",
    url = "https://m.diplom.de/document/219963"
}