The SOURCE Registry: what is the learning curve in transapical aortic valve implantation? Eur J Cardiothorac Surg 5 January Jan 2011 15 years ago Wendler O, Walther T, Schroefel H, Lange R, Treede H, Fusari M, Rubino P, Thomas M http://www.ncbi.nlm.nih.gov/pubmed/21183357
