Kettler, A., Rohlmann, F., Neidlinger-Wilke, C., Werner, K., Claes, L., & Wilke, H. (2006). Validity and interobserver agreement of a new radiographic grading system for intervertebral disc degeneration: Part II. Cervical spine. Springer-Verlag.

Kettler, Annette, Friederike Rohlmann, Cornelia Neidlinger-Wilke, Karin Werner, Lutz Claes, and Hans-Joachim Wilke. Validity and Interobserver Agreement of a New Radiographic Grading System for Intervertebral Disc Degeneration: Part II. Cervical Spine. Springer-Verlag, 2006.

Kettler, Annette, et al. Validity and Interobserver Agreement of a New Radiographic Grading System for Intervertebral Disc Degeneration: Part II. Cervical Spine. Springer-Verlag, 2006.