1. Aarås, A., 1987. Postural load and the development of musculoskeletal illness. Thesis, Institute of Work Physiology, Oslo.
2. Epidemiologic aspects on low/back pain in industry;Andersson;Spine,1981
3. Statistical Methods in Medical Research;Armitage,1994
4. Methods for evaluation of muscle strength;Asmussen;Communications of the National Association of Infantile Paralysis,1959
5. Muscles alive, their function revealed by electromyography;Basmajian,1995