@book { LudwigGelpke18971982,
    title = "Ludwig Gelpke (1897-1982)",
    subtitle = "Studien zum Werk- Werkverzeichnis der Gemälde",
    author = "Corinna {Thierolf}",
    year = "1994",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1113930"
}