@book { DerWienerKongress,
    title = "Der Wiener Kongress",
    author = "Sven {Lachhein}",
    year = "2008",
    publisher = "GRIN Verlag",
    address = "München, Germany",
    doi = "10.3239/9783638025362",
    url = "https://www.hausarbeiten.de/document/89046"
}