The ”ELITE” model: construct validation of a new training system for natural orifice transluminal endoscopic surgery (NOTES) - Gillen, S.; Wilhelm, D.; Meining, A.; Fiolka, A.; Doundoulakis, E.; Schneider, A.; Delius, S. von; Friess, H.; Feussner, H. (Endoscopy, 2009)