@book { AbnehmenmitderMinus20Regel,
    title = "Abnehmen mit der Minus-20%-Regel",
    author = "Sven {Bach} and Benjamin {Breitmaier}",
    year = "2019",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/451607"
}