@book { DaseinheitlicheSchulsystemderDDR,
    title = "Das einheitliche Schulsystem der DDR",
    author = "Susan {Kallmeyer}",
    year = "2000",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638961431",
    url = "https://www.hausarbeiten.de/document/97691"
}