@book { DieUmsatzsteuerreform1999,
    title = "Die Umsatzsteuerreform 1999",
    author = "Andreas {Bolik}",
    year = "2000",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832420574",
    url = "https://m.diplom.de/document/217485"
}