@book { LanguageasChiffre,
    title = "Language as Chiffre",
    subtitle = "Wittgenstein’s Theory of Symbols",
    author = "Ulrike {Ritter}",
    year = "2001",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1091288"
}