@book { DieSchlachtvonGettysburg,
    title = "Die Schlacht von Gettysburg",
    author = "Stephan Ernst {Maurer}",
    year = "2023",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b20461",
    url = "https://www.peterlang.com/document/1292360"
}