@book { DerGestaltpsychologeKarlDuncker,
    title = "Der Gestaltpsychologe Karl Duncker",
    author = "Sören {Wendelborn}",
    year = "2003",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1097065"
}