1. Angevin JB (1973) Clinically relevant embryology of the vertebral column and spinal cord. Clin Neurosurg 20:95
2. Hensinger RN (1989) Congenital anomalies of the odontoid. In: Cervical Spine Research Society (ed) The cervical spine, 2nd ed. Lippincott, Philadelphia, p 248
3. Noback CR, Robertson GG (1951) Sequences of appearance of ossification centres in the human skeleton during the first five pre-natal months. Am J Anat 89(1):1
4. Ogden JA, Grogan DP (1987) The scientific basis of orthopaedics, 2nd edn. Appleton and Lange, Norwalk, pp 55–69
5. O’Rahilly R, Muller E, Meyer DB (1983) The human vertebral column at the end of the embryonic period proper. The occipitocervical region. J Anat 136:181–195