@book { DiefriedlicheRevolution198990inHalleSaale,
    title = "Die friedliche Revolution 1989/90 in Halle/Saale",
    author = "Sebastian {Stude}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1106830"
}