| APA | Smart Define. (2011). hierarchical classification system thesaurus. Retrieved September 21, 2026, from https://smartdefine.org/hierarchical_classification_system/thesaurus/broader |
| Chicago | Smart Define. 2011. "hierarchical classification system thesaurus" https://smartdefine.org/hierarchical_classification_system/thesaurus/broader (accessed September 21, 2026). |
| Harvard | Smart Define 2011, hierarchical classification system thesaurus, Smart Define, viewed 21 September, 2026, <https://smartdefine.org/hierarchical_classification_system/thesaurus/broader>. |
| MLA | Smart Define. "hierarchical classification system thesaurus" 26 April 2011. Web. 21 September 2026. <https://smartdefine.org/hierarchical_classification_system/thesaurus/broader> |