1. Acute low back pain in industry. A controlled prospective study with special reference to therapy and confounding factors;Berguist-Ullman;Acta Orthop Scand (Suppl),1977
2. Low back trouble in a general population of 30-,40-,50- and 60-years old men and women. Study design, representativeness and basic results;Biering-Sorenson;Dan. Med. Bull.,1982
3. Lifting as an industrial hazard;Brown,1971
4. Occupational Biomechanics;Chaffin,1984
5. Prevention of back pain;Glover,1976