@book { DasDeutscheVolksliedarchivFreiburgimBreisgau,
    title = "Das Deutsche Volksliedarchiv Freiburg im Breisgau",
    author = "Otto {Holzapfel}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    url = "https://www.peterlang.com/document/1078801"
}