@book { WasisteinMenhir,
    title = "Was ist ein Menhir?",
    author = "Ernst {Probst}",
    year = "2011",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783656085737",
    url = "https://www.hausarbeiten.de/document/183871"
}