@book { GeometrischeFigurenTangram,
    title = "Geometrische Figuren - Tangram",
    author = "Stephanie {Müller}",
    year = "2008",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638051385",
    url = "https://www.hausarbeiten.de/document/90761"
}