| APA | Smart Define. (2013). past progressive thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/past_progressive/thesaurus/related |
| Chicago | Smart Define. 2013. "past progressive thesaurus" https://smartdefine.org/past_progressive/thesaurus/related (accessed September 26, 2026). |
| Harvard | Smart Define 2013, past progressive thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/past_progressive/thesaurus/related>. |
| MLA | Smart Define. "past progressive thesaurus" 18 May 2013. Web. 26 September 2026. <https://smartdefine.org/past_progressive/thesaurus/related> |