@book { StaufischeLehnspolitik,
    title = "Staufische Lehnspolitik",
    subtitle = "am Ende des 12. Jahrhunderts 1180-1197",
    author = "Sigrid {Hauser}",
    year = "1998",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1086240"
}