@book { RckenohneSchmerz,
    title = "Rücken ohne Schmerz",
    subtitle = "Die besten Tipps zur schnellen Selbsthilfe, 5x5 Übungen, die wirklich helfen",
    author = "Dr. Felix {Söller} and Ellen {Warstat}",
    year = "2019",
    publisher = "humboldt",
    address = "Hannover, Deutschland",
    url = "https://schluetersche.openpublishing.com/document/456357"
}