@book { DerunbefristeteWiderrufinternetbasierterVertrge,
    title = "Der unbefristete Widerruf internetbasierter Verträge",
    author = "Rainer Jürgen {Scharf}",
    year = "2021",
    publisher = "Peter Lang Verlag",
    address = "Berlin, Germany",
    url = "https://www.peterlang.com/document/1107228"
}