@book { HeinrichHeinesBuchderLieder,
    title = "Heinrich Heines Buch der Lieder",
    author = "Rolf {Lüdi}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    url = "https://www.peterlang.com/document/1070910"
}