| APA | Smart Define. (2015). efficacious thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/efficacious/thesaurus/antonyms |
| Chicago | Smart Define. 2015. "efficacious thesaurus" https://smartdefine.org/efficacious/thesaurus/antonyms (accessed September 23, 2026). |
| Harvard | Smart Define 2015, efficacious thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/efficacious/thesaurus/antonyms>. |
| MLA | Smart Define. "efficacious thesaurus" 13 October 2015. Web. 23 September 2026. <https://smartdefine.org/efficacious/thesaurus/antonyms> |