Did survival improve after the implementation of intraoperative neuronavigation and 3D ultrasound in glioblastoma surgery? A retrospective analysis of 192 primary operations - Sæther, C A; Torsteinsen, M; Torp, S H; Sundstrøm, S; Unsgård, G; Solheim, O (J Neurol Surg A Cent Eur Neurosurg, 2012)