Aetiology of Ludwig van Beethoven's hearing impairment: hypotheses over the past 100 years - A systematic review. - Thomas JP; Dazert S; Prescher A; Voelter C (European archives of oto-rhino-laryngology : official journal of the European Federation of Oto-Rhino-Laryngological Societies (EUFOS) : affiliated with the German Society for Oto-Rhino-Laryngology - Head and Neck Surgery, 2021)