@book { GesunderSchlaf, title = "Gesunder Schlaf", subtitle = "Endlich wieder gut schlafen", author = "Dr. med. Guido {Ern} and Dr. med. Ralf D. {Fischbach}", year = "2010", publisher = "humboldt", address = "Hannover, Deutschland", url = "https://schluetersche.openpublishing.com/document/403392" }