@book { DieKonkordatseheinSpanien,
    title = "Die Konkordatsehe in Spanien",
    author = "Sabine {Konrad}",
    year = "2019",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b15330",
    url = "https://www.peterlang.com/document/1050022"
}