Harmer, Greg; Derek Abbott (2005). "The Feynman-Smoluchowski ratchet". Parrondo's Paradox Research Group. School of Electrical & Electronic Engineering, Univ. of Adelaide. Archived from the original on 2009-10-11. Retrieved 2010-01-15.
Parrondo, Juan M. R.; Pep Español (March 8, 1996). "Criticism of Feynman's analysis of the ratchet as an engine". American Journal of Physics. 64 (9): 1125. Bibcode:1996AmJPh..64.1125P. doi:10.1119/1.18393.
Parrondo, Juan M. R.; Pep Español (March 8, 1996). "Criticism of Feynman's analysis of the ratchet as an engine". American Journal of Physics. 64 (9): 1125. Bibcode:1996AmJPh..64.1125P. doi:10.1119/1.18393.
Harmer, Greg; Derek Abbott (2005). "The Feynman-Smoluchowski ratchet". Parrondo's Paradox Research Group. School of Electrical & Electronic Engineering, Univ. of Adelaide. Archived from the original on 2009-10-11. Retrieved 2010-01-15.