@book { LehrwerkeundihreAlternativen,
    title = "Lehrwerke und ihre Alternativen",
    author = "Renate {Fery} and Volker {Raddatz}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1090000"
}