| APA | Smart Define. (2015). dead letter thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/dead_letter/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "dead letter thesaurus" https://smartdefine.org/dead_letter/thesaurus/synonyms (accessed September 21, 2026). |
| Harvard | Smart Define 2015, dead letter thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/dead_letter/thesaurus/synonyms>. |
| MLA | Smart Define. "dead letter thesaurus" 10 April 2015. Web. 21 September 2026. <https://smartdefine.org/dead_letter/thesaurus/synonyms> |