D. Wiedemann, N. Bonaros, G. Feuchtner, J. Bonatti, and T. Schachner, “Difficulties in Beating-Heart Totally Endoscopic Coronary Artery Bypass Grafting: How to Handle the Problem Endoscopically”, HSF, vol. 12, no. 3, pp. E141-E142, Jun. 2009.