@book { KonzeptionundEntwicklungeinesmobilenStadtfhrers,
    title = "Konzeption und Entwicklung eines mobilen Stadtführers",
    author = "Christian {Halbach}",
    year = "2006",
    publisher = "Diplom.de",
    address = "Hamburg, Deutschland",
    doi = "10.3239/9783832492915",
    url = "https://m.diplom.de/document/224413"
}