@book { PolenimErstenWeltkrieg,
    title = "Polen im Ersten Weltkrieg",
    author = "Hartmut Michael {Kühn}",
    year = "2019",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b14744",
    url = "https://www.peterlang.com/document/1057232"
}