@book { BeschwerdemanagementimTourismussektor,
    title = "Beschwerdemanagement im Tourismussektor",
    author = "Andreas {Mertes}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832443207",
    url = "https://m.diplom.de/document/219922"
}