Study on accuracy and interobserver reliability of the assessment of odontoid fracture union using plain radiographs or CT scans - Koller, H; Kolb, K; Zenner, J; Reynolds, J; Dvorak, M; Acosta, F; Forstner, R; Mayer, M; Tauber, M; Auffarth, A; Kathrein, A; Hitzl, W (Eur Spine J, 2009)