@book { UmlagefinanzierteAlterssicherungLandundMigration,
    title = "Umlagefinanzierte Alterssicherung, Land und Migration",
    author = "Ulrich {Hange}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1091890"
}