@book { ComparativeAnalysisofDepartmentStoresandShoppingCentersinGermanyandSpain,
    title = "Comparative Analysis of Department Stores and Shopping Centers in Germany and Spain",
    author = "Christoph {Wappler}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832498153",
    url = "https://m.diplom.de/document/224932"
}