@book { DasBaugebietinderaargauischenOrtsplanung,
    title = "Das Baugebiet in der aargauischen Ortsplanung",
    author = "Karl {Frey}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Lausanne, Switzerland",
    url = "https://www.peterlang.com/document/1070002"
}