| APA | Smart Define. (2013). hard as stone thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/hard_as_stone/thesaurus/related |
| Chicago | Smart Define. 2013. "hard as stone thesaurus" https://smartdefine.org/hard_as_stone/thesaurus/related (accessed September 30, 2026). |
| Harvard | Smart Define 2013, hard as stone thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/hard_as_stone/thesaurus/related>. |
| MLA | Smart Define. "hard as stone thesaurus" 19 May 2013. Web. 30 September 2026. <https://smartdefine.org/hard_as_stone/thesaurus/related> |