1. Bao, S. (1992).Physical work load and musculoskeletal disorders among Chinese assembly workers.Unpublished licentiate thesis, Lulcå University of Technology, Luleå, Sweden.
2. Hernberg, S. (1991).Introduction to occupational epidemiology.Chelsea, MI, USA: Lewis Publishers.
3. Hildebrandt, V.H. (1987). A review of epidemiological research on risk factors of low back pain. In P. Buckle (Ed.),Musculoskeletal disorders at work(pp. 9–16). London, UK: Taylor & Francis.
4. Jayson, M.I.V. (1980).The lumbar spine and back pain(2nd ed.). New York, NY, USA: Pitman.
5. Li, T. & Lu, X. (1994).Work-related chronic musculoskeletal disorders.Unpublished manuscript, Chinese Academy of Preventive Medicine, Beijing, China.