@book { DiePapstwahldesJahres1903,
    title = "Die Papstwahl des Jahres 1903",
    author = "Peter {Frei}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    url = "https://www.peterlang.com/document/1070122"
}