@book { InternationaleMarkterschlieungamBeispielvonCoffeeShops,
    title = "Internationale Markterschließung am Beispiel von Coffee-Shops",
    author = "Constanze {Ullmann}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832482237",
    url = "https://m.diplom.de/document/223439"
}