@book { DasHamburgerModell,
    title = "Das Hamburger Modell",
    author = "Belma {Gündüz}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640962310",
    url = "https://www.hausarbeiten.de/document/175303"
}