| APA | Smart Define. (2015). formidable thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/formidable/thesaurus/antonyms |
| Chicago | Smart Define. 2015. "formidable thesaurus" https://smartdefine.org/formidable/thesaurus/antonyms (accessed September 22, 2026). |
| Harvard | Smart Define 2015, formidable thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/formidable/thesaurus/antonyms>. |
| MLA | Smart Define. "formidable thesaurus" 17 July 2015. Web. 22 September 2026. <https://smartdefine.org/formidable/thesaurus/antonyms> |