@book { Gragas,
    title = "Gragas",
    subtitle = "Graphemische Untersuchungen zur Handschrift GKS 1157 Fol.",
    author = "Hans {Fix}",
    year = "1980",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1072257"
}