@book { DiefrumenedlenPuren,
    title = "Die frumen edlen Puren",
    subtitle = "Untersuchung zum Stilzusammenhang zwischen den historischen Volksliedern der alten Eidgenossenschaft und der deutschen Heldenepik",
    author = "Viktor {Schlumpf}",
    year = "1969",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    url = "https://www.peterlang.com/document/1069283"
}