@book { CityManagementinDeutschland,
    title = "City-Management in Deutschland",
    author = "Torsten {Petersen}",
    year = "2000",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832422028",
    url = "https://m.diplom.de/document/218026"
}