@book { CityMarketingCottbus,
    title = "City-Marketing Cottbus",
    author = "Sindy {Rentsch}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832479787",
    url = "https://m.diplom.de/document/223004"
}