Primary Endoscopy/Endoscopic Ultrasound (WUS) Versus Primary Endoscopy Plus Transabdominal Ultrasound (TUS) in the Work-Up of Patients with Upper Abdominal Pain (UAP): Final Results of a Prospective Multi-Center-Study. - Chang,K.J.; Chak,A.; Lightdale,C. (Gastrointest Endosc, 2005)