| APA | Smart Define. (2011). ernst heinrich haeckel thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/ernst_heinrich_haeckel/thesaurus/broader |
| Chicago | Smart Define. 2011. "ernst heinrich haeckel thesaurus" https://smartdefine.org/ernst_heinrich_haeckel/thesaurus/broader (accessed September 30, 2026). |
| Harvard | Smart Define 2011, ernst heinrich haeckel thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/ernst_heinrich_haeckel/thesaurus/broader>. |
| MLA | Smart Define. "ernst heinrich haeckel thesaurus" 26 April 2011. Web. 30 September 2026. <https://smartdefine.org/ernst_heinrich_haeckel/thesaurus/broader> |