1. Amontons, G. (1699). De la résistance causée dans les machines. Mémoires de l’Académie Royale A, 12, 257–282.
2. ASTM International. (2010). Standard test method for linearly reciprocating ball-on-flat sliding wear, ASTM G 133-05.
3. Bahadur, S. (2004). Friction and wear of polymers and composites. In J. Vizintin, M. Kalin, K. Dohda, & S. Jahamir (Eds.), Tribology of Mechanical Systems (pp. 239–265). New York: ASME Press.
4. Bill Gates. (2013). Robots will be the next world-changing technology,
http://finance.yahoo.com/news/bill-gates-robots-next-world-134500596.html
5. Bi, Z. M. (2013). Design of a spherical parallel kinematic machine for ankle rehabilitation. Advanced Robotics, 27(2), 121–132.