title: Introduction.
authors: University of Missouri-Columbia School of Medicine, Dept. of Physical Medicine and Rehabilitation, 5R01 Rusk Rehabilitation Center, One Hospital Drive, Columbia, MO 65212, USA.
authors: B
authors: B
authors: Johnstone
authors: University of Florida, College of Health Related Professions, Health Science Center, Room N1-2, P.O. Box 100185 HSC, Gainesville, FL 32610-0185, USA.
authors: R G
authors: RG
authors: Frank