@book { SchlsselqualifikationSprache,
    title = "Schlüsselqualifikation Sprache",
    subtitle = "Anforderungen – Standards – Vermittlung",
    author = "Friedrich {Lenz}",
    year = "2009",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1106694"
}