@book { DieschnstenBalladen,
    title = "Die schönsten Balladen",
    author = "Sibylle {Frees}",
    year = "2013",
    publisher = "dotbooks Verlag",
    address = "München, Deutschland",
    doi = "10.3239/9783955202521",
    url = "https://m.dotbooks.de/document/212948"
}