@book { BrechtsShne,
    title = "Brechts Söhne",
    author = "Wolfgang {Conrad} and Ernst-Ullrich {Pinkert} and Erich {Unglaub}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1105576"
}