| APA | Smart Define. (2015). impervious thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/impervious/thesaurus/narrower |
| Chicago | Smart Define. 2015. "impervious thesaurus" https://smartdefine.org/impervious/thesaurus/narrower (accessed September 22, 2026). |
| Harvard | Smart Define 2015, impervious thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/impervious/thesaurus/narrower>. |
| MLA | Smart Define. "impervious thesaurus" 14 April 2015. Web. 22 September 2026. <https://smartdefine.org/impervious/thesaurus/narrower> |