@book { DiePlanungszelleundihreUmwelt,
    title = "Die Planungszelle und ihre Umwelt",
    author = "Detlef {Garbe}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1071789"
}