@book { SozialeSchichtunginPolen,
    title = "Soziale Schichtung in Polen",
    author = "Susann {Schulze}",
    year = "2008",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783640107742",
    url = "https://www.hausarbeiten.de/document/112104"
}