@book { DasPlanspiel,
    title = "Das Planspiel",
    author = "Nils {Becker} and Daria {Bayer}",
    year = "2003",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638227216",
    url = "https://www.hausarbeiten.de/document/18354"
}