| APA | Smart Define. (2011). perpetual motion machine thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/perpetual_motion_machine/thesaurus/broader |
| Chicago | Smart Define. 2011. "perpetual motion machine thesaurus" https://smartdefine.org/perpetual_motion_machine/thesaurus/broader (accessed September 21, 2026). |
| Harvard | Smart Define 2011, perpetual motion machine thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/perpetual_motion_machine/thesaurus/broader>. |
| MLA | Smart Define. "perpetual motion machine thesaurus" 26 April 2011. Web. 21 September 2026. <https://smartdefine.org/perpetual_motion_machine/thesaurus/broader> |