@book { Stdtemarketing,
    title = "Städtemarketing",
    author = "Ulrich {Ehmes}",
    year = "2001",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832435356",
    url = "https://m.diplom.de/document/219197"
}