@book { Freiheit,
    title = "Freiheit",
    subtitle = "Begriff und Bedeutung in Geschichte und Gegenwart",
    author = "André {Mercier}",
    year = "1974",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    url = "https://www.peterlang.com/document/1112971"
}