Balloon-Assisted Endoscopic Retroperitoneal Gasless Approach (BERG) for Lumbar Interbody Fusion: Is it a Valid Alternative to the Laparoscopic Approach? - Gazzeri, R; Tamorri, M; Galarza, M; Faiola, A; Gazzeri, G (min - Minimally Invasive Neurosurgery, 2007)