| APA | Smart Define. (2015). hardness thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/hardness/thesaurus/related |
| Chicago | Smart Define. 2015. "hardness thesaurus" https://smartdefine.org/hardness/thesaurus/related (accessed September 26, 2026). |
| Harvard | Smart Define 2015, hardness thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/hardness/thesaurus/related>. |
| MLA | Smart Define. "hardness thesaurus" 14 April 2015. Web. 26 September 2026. <https://smartdefine.org/hardness/thesaurus/related> |