↑ Wheel and Axle, The World Book Encyclopedia, World Book Inc., 1998, pp. 280-281 ↑ Uloser, Abbott Payson (1988). A History of Mechanical Inventions. USA: Courier Dover Publications. p. 98. ISBN 048625593X. ↑ Elroy McKendree Avery, Elementary Physics, New York : Sheldon & Company, 1878. 1 2 Bowser, Edward Albert, 1890, An elementary treatise on analytic mechanics: with numerous examples. (Originally from the University of Michigan) D. Van Nostrand Company, pp. 190 ↑ Anthony, David A. (2007). The horse, the wheel, and language: how Bronze-Age riders from the Eurasian steppes shaped the modern world. Princeton, N.J: Princeton University Press. p. 67. ISBN 0-691-05887-3. ↑ Aleksander Gasser (March 2003). "World's Oldest Wheel Found in Slovenia". Government Communication Office of the Republic of Slovenia. Retrieved 19 August 2010. ↑ Prater, Edward L. (1994), Basic Machines, Naval Education and Training Professional Development and Technology Center, NAVEDTRA 14037 ↑ Bureau of Naval Personnel, 1971, Basic Machines and How They Work, Dover Publications. ↑ J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, Theory of Machines and Mechanisms, Oxford University Press, New York. ↑ Baker, C.E. The Principles and Practice of Statics and Dynamics … for the Use of Schools and Private Students. London: John Weale, 59, High Holborn. 1851 pp. 26-29 read online or download full text