| APA | Smart Define. (1970). serious problem thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/serious_problem/thesaurus/synonyms |
| Chicago | Smart Define. 1970. "serious problem thesaurus" https://smartdefine.org/serious_problem/thesaurus/synonyms (accessed September 22, 2026). |
| Harvard | Smart Define 1970, serious problem thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/serious_problem/thesaurus/synonyms>. |
| MLA | Smart Define. "serious problem thesaurus" 1 January 1970. Web. 22 September 2026. <https://smartdefine.org/serious_problem/thesaurus/synonyms> |