| APA | Smart Define. (2015). impregnability thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/impregnability/thesaurus/antonyms |
| Chicago | Smart Define. 2015. "impregnability thesaurus" https://smartdefine.org/impregnability/thesaurus/antonyms (accessed September 20, 2026). |
| Harvard | Smart Define 2015, impregnability thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/impregnability/thesaurus/antonyms>. |
| MLA | Smart Define. "impregnability thesaurus" 14 April 2015. Web. 20 September 2026. <https://smartdefine.org/impregnability/thesaurus/antonyms> |