| APA | Smart Define. (2013). parts per million thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/parts_per_million/thesaurus/synonyms |
| Chicago | Smart Define. 2013. "parts per million thesaurus" https://smartdefine.org/parts_per_million/thesaurus/synonyms (accessed September 30, 2026). |
| Harvard | Smart Define 2013, parts per million thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/parts_per_million/thesaurus/synonyms>. |
| MLA | Smart Define. "parts per million thesaurus" 18 May 2013. Web. 30 September 2026. <https://smartdefine.org/parts_per_million/thesaurus/synonyms> |