| APA | Smart Define. (1970). pen pals thesaurus. Retrieved September 20, 2026, from https://smartdefine.org/pen_pals/thesaurus/synonyms |
| Chicago | Smart Define. 1970. "pen pals thesaurus" https://smartdefine.org/pen_pals/thesaurus/synonyms (accessed September 20, 2026). |
| Harvard | Smart Define 1970, pen pals thesaurus, Smart Define, viewed 20 September, 2026, <https://smartdefine.org/pen_pals/thesaurus/synonyms>. |
| MLA | Smart Define. "pen pals thesaurus" 1 January 1970. Web. 20 September 2026. <https://smartdefine.org/pen_pals/thesaurus/synonyms> |