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