@book { RussischundUkrainischimWandel,
    title = "Russisch und Ukrainisch im Wandel",
    author = "Olga {Flug}",
    year = "2019",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b15726",
    url = "https://www.peterlang.com/document/1110971"
}