| APA | Smart Define. (2013). sign of past thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/sign_of_past/thesaurus/synonyms |
| Chicago | Smart Define. 2013. "sign of past thesaurus" https://smartdefine.org/sign_of_past/thesaurus/synonyms (accessed September 23, 2026). |
| Harvard | Smart Define 2013, sign of past thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/sign_of_past/thesaurus/synonyms>. |
| MLA | Smart Define. "sign of past thesaurus" 17 May 2013. Web. 23 September 2026. <https://smartdefine.org/sign_of_past/thesaurus/synonyms> |