@book { VariablisierungvonFixkostendurchFacilityManagement,
    title = "Variablisierung von Fixkosten durch Facility Management",
    author = "Philipp {Kaufmann}",
    year = "2002",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832453763",
    url = "https://m.diplom.de/document/220938"
}