@book { SupplySidePolicyindenUSA,
    title = "Supply-Side Policy in den USA",
    author = "Joachim {Nagel}",
    year = "2018",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    doi = "10.3726/b13797",
    url = "https://www.peterlang.com/document/1068372"
}