@book { BusinessPlanReusableBallerinasforDiscos,
    title = "Business Plan: Reusable Ballerinas for Discos",
    author = "Mario {Kempf}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640922680",
    url = "https://www.hausarbeiten.de/document/172391"
}