Sugar, Thomas G.; Armstrong, David; Najafi, Bijan; Redkar, Sangram; Ward, Jeffrey A.: 'Lower-limb wearable robotics' (Control, Robotics and Sensors, 2018), 'Wearable Exoskeleton Systems: Design, control and applications', Chap. 1, pp. 5-23, DOI: 10.1049/PBCE108E_ch1
IET Digital Library, https://digital-library.theiet.org/;jsessionid=6te99jteh4i6v.x-iet-live-01content/books/10.1049/pbce108e_ch1