Dusing, S. C., & Harbourne, R. T. (2010). Variability in Postural Control During Infancy: Implications for Development, Assessment, and Intervention. Physical Therapy, 90(12), 1838–1849. http://doi.org/10.2522/ptj.2010033

Stergiou N, Harbourne R, Cavanaugh J. Optimal movement variability: a new theoretical perspective for neurologic physical therapy. J Neurol Phys Ther. 2006 Sep;30(3):120-9. PubMed PMID: 17029655.

Fetters L. Perspective on variability in the development of human action. Phys Ther. 2010 Dec;90(12):1860-7. doi: 10.2522/ptj.2010090. Epub 2010 Oct 21.  https://doi.org/10.2522/ptj.2010090

Kyvelidou, A., Harbourne, R. T., & Stergiou, N. (2010). Severity and Characteristics of Developmental Delay Can Be Assessed Using Variability Measures of Sitting Posture. Pediatric Physical Therapy : The Official Publication of the Section on Pediatrics of the American Physical Therapy Association, 22(3), 259–266. http://doi.org/10.1097/PEP.0b013e3181ea75f1

Westcott SL, Burtner PA. Postural control in children: implications for pediatric practice. Phys Occup Ther Pediatr. 2004;24(1-2):5-55. Review. PubMed PMID: 15268997.