@book { WasistdemBrgerzuzumuten,
    title = "Was ist dem Bürger zuzumuten?",
    subtitle = "Sprachpflege im 21. Jahrhundert",
    author = "Karl-Ernst {Sommerfeldt}",
    year = "2009",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1106485"
}