| APA | Smart Define. (2011). doctor of philosophy thesaurus. Retrieved September 30, 2026, from https://smartdefine.org/doctor_of_philosophy/thesaurus/narrower |
| Chicago | Smart Define. 2011. "doctor of philosophy thesaurus" https://smartdefine.org/doctor_of_philosophy/thesaurus/narrower (accessed September 30, 2026). |
| Harvard | Smart Define 2011, doctor of philosophy thesaurus, Smart Define, viewed 30 September, 2026, <https://smartdefine.org/doctor_of_philosophy/thesaurus/narrower>. |
| MLA | Smart Define. "doctor of philosophy thesaurus" 26 April 2011. Web. 30 September 2026. <https://smartdefine.org/doctor_of_philosophy/thesaurus/narrower> |