| APA | Smart Define. (2011). willem de sitter thesaurus. Retrieved September 28, 2026, from https://smartdefine.org/willem_de_sitter/thesaurus/synonyms |
| Chicago | Smart Define. 2011. "willem de sitter thesaurus" https://smartdefine.org/willem_de_sitter/thesaurus/synonyms (accessed September 28, 2026). |
| Harvard | Smart Define 2011, willem de sitter thesaurus, Smart Define, viewed 28 September, 2026, <https://smartdefine.org/willem_de_sitter/thesaurus/synonyms>. |
| MLA | Smart Define. "willem de sitter thesaurus" 26 April 2011. Web. 28 September 2026. <https://smartdefine.org/willem_de_sitter/thesaurus/synonyms> |