@book { Krampfadernnatrlichbehandeln,
    title = "Krampfadern natürlich behandeln",
    author = "Theresia {Wilhelms}",
    year = "2021",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/403097"
}