@book { WalterDahnPreparingfortheFuture,
    title = "Walter Dahn- «Preparing for the Future»",
    author = "Marietta {Franke}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1109505"
}