| APA | Smart Define. (2011). periwinkle plant derivative thesaurus. Retrieved September 29, 2026, from https://smartdefine.org/periwinkle_plant_derivative/thesaurus/narrower |
| Chicago | Smart Define. 2011. "periwinkle plant derivative thesaurus" https://smartdefine.org/periwinkle_plant_derivative/thesaurus/narrower (accessed September 29, 2026). |
| Harvard | Smart Define 2011, periwinkle plant derivative thesaurus, Smart Define, viewed 29 September, 2026, <https://smartdefine.org/periwinkle_plant_derivative/thesaurus/narrower>. |
| MLA | Smart Define. "periwinkle plant derivative thesaurus" 26 April 2011. Web. 29 September 2026. <https://smartdefine.org/periwinkle_plant_derivative/thesaurus/narrower> |