Burkman, J. ., Grindle, G. ., Wang, H. ., Kelleher, A. ., & Cooper, R. . (1969). Further Development of a Robotic-Assisted Transfer Device. Topics in Spinal Cord Injury Rehabilitation, 23(2), 140-146. https://doi.org/10.1310/sci2302-140 (Original work published 1969)

Candiotti, J. ., Sundaram, S. ., Daveler, B. ., Gebrosky, B. ., Grindle, G. ., Wang, H. ., & Cooper, R. . (1969). Kinematics and Stability Analysis of a Novel Power Wheelchair When Traversing Architectural Barriers. Topics in Spinal Cord Injury Rehabilitation, 23(2), 110-119. https://doi.org/10.1310/sci2302-110 (Original work published 1969)