1. Bar-Or, O., Skinner, J. S., Buskirk, E. R., Borg, G. A. V.: Physiological and perceptual indicators of physical stress in 41- to 60-year-old men who vary in conditioning level and in body fatness. Med. Sci. Sports 4, 96?100 (1972)
2. Borg, G. A. V.: Physical performance and perceived exertion. Lund: Gleerups 1962
3. Borg, G. A. V., Linderholm, H.: Perceived exertion and pulse rate during graded exercise in various age groups. Acta. Med. Scand. [Suppl.] 472, 194 (1967)
4. Bolterman, B. R., Binder, M. D., Stuart, D. G.: Functional anatomy of the association between motor unit and muscle receptors. Am. Zool. (in press) (1978)
5. Burke, R. E., Levine, D. N., Zajac, F. E., Isairis, P., Engel, W. K.: Mammalian motor units: Physiological-histochemical correlation in three types in cat gastronemius. Science 14, 709?712 (1971)