@book { WaswissenwirberdieSteinzeit,
    title = "Was wissen wir über die Steinzeit?",
    author = "Ernst {Probst}",
    year = "2012",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656232308",
    url = "https://www.hausarbeiten.de/document/195529"
}