@book { RegionaleKartensystemeimTourismus,
    title = "Regionale Kartensysteme im Tourismus",
    author = "Tim {Schwärmer}",
    year = "2004",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832480714",
    url = "https://m.diplom.de/document/223299"
}