@book { GustavMahlerunddasLied,
    title = "Gustav Mahler und das Lied",
    author = "Bernd {Sponheuer} and Wolfram {Steinbeck}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1095118"
}