1. Hildebrandt, G., Rohmert, W., and Rutenfranz, J., Int. J. Chronobiol.2 (1974) 175.
2. Bjerner, B., and Swensson, A., Acta med. scand. Suppl.278 (1953) 102.
3. Prokop, O., and Prokop, L., Dt. Z. ges. gericht. Med.44 (1955) 343.
4. Folkard, S., Monk, T.H., and Lobban, M.C., Ergonomics 21 (1978) 785.
5. Colquhoun, W.P., Blake, M.J.F., and Edwards, R.S., Ergonomics11 (1968) 437.