@book { MalteserkreuzundPreuenadler,
    title = "Malteserkreuz und Preußenadler",
    author = "Urs {Buhlmann}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1088938"
}