@book { OffenerUnterrichtinderGrundschule,
    title = "Offener Unterricht in der Grundschule",
    author = "Saskia {Pfeil}",
    year = "2012",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656167815",
    url = "https://www.hausarbeiten.de/document/191809"
}