| APA | Smart Define. (2016). challenging thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/challenging/thesaurus/antonyms |
| Chicago | Smart Define. 2016. "challenging thesaurus" https://smartdefine.org/challenging/thesaurus/antonyms (accessed September 22, 2026). |
| Harvard | Smart Define 2016, challenging thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/challenging/thesaurus/antonyms>. |
| MLA | Smart Define. "challenging thesaurus" 2 March 2016. Web. 22 September 2026. <https://smartdefine.org/challenging/thesaurus/antonyms> |