@book { VierzigJahreinWestBerlinundimOsten,
    title = "Vierzig Jahre in West-Berlin – und im «Osten»",
    author = "Jürgen {Boeckh}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1135704"
}