@book { Geschenktumsonstgegeben,
    title = "Geschenkt – umsonst gegeben?",
    author = "Michael {Rosenberger} and Ferdinand {Reisinger} and Ansgar {Kreutzer}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1101574"
}