@book { DasPlusquamperfektumimPolnischen,
    title = "Das Plusquamperfektum im Polnischen",
    author = "Jadwiga {Maurer}",
    year = "1960",
    publisher = "Biblion",
    address = ", Germany",
    doi = "10.3726/b12341",
    url = "https://www.peterlang.com/document/1066836"
}