@book { OffenerUnterricht,
    title = "Offener Unterricht",
    author = "Andrea {Finke}",
    year = "2005",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638389075",
    url = "https://www.hausarbeiten.de/document/40384"
}