@book { DoppelstaatDDR,
    title = "Doppelstaat DDR",
    subtitle = "Menschenrechtsverletzungen der Deutschen Volkspolizei",
    author = "Hans-Michael {Brey}",
    year = "1999",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1088390"
}