| APA | Smart Define. (2013). hardhead thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/hardhead/thesaurus/synonyms |
| Chicago | Smart Define. 2013. "hardhead thesaurus" https://smartdefine.org/hardhead/thesaurus/synonyms (accessed September 22, 2026). |
| Harvard | Smart Define 2013, hardhead thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/hardhead/thesaurus/synonyms>. |
| MLA | Smart Define. "hardhead thesaurus" 17 June 2013. Web. 22 September 2026. <https://smartdefine.org/hardhead/thesaurus/synonyms> |