| APA | Smart Define. (1970). Perls' Prussian blue thesaurus. Retrieved September 22, 2026, from https://smartdefine.org/perls%27_prussian_blue/thesaurus/broader |
| Chicago | Smart Define. 1970. "Perls' Prussian blue thesaurus" https://smartdefine.org/perls%27_prussian_blue/thesaurus/broader (accessed September 22, 2026). |
| Harvard | Smart Define 1970, Perls' Prussian blue thesaurus, Smart Define, viewed 22 September, 2026, <https://smartdefine.org/perls%27_prussian_blue/thesaurus/broader>. |
| MLA | Smart Define. "Perls' Prussian blue thesaurus" 1 January 1970. Web. 22 September 2026. <https://smartdefine.org/perls%27_prussian_blue/thesaurus/broader> |