| APA | Smart Define. (2016). doubtfulness thesaurus. Retrieved September 23, 2026, from https://smartdefine.org/doubtfulness/thesaurus/narrower |
| Chicago | Smart Define. 2016. "doubtfulness thesaurus" https://smartdefine.org/doubtfulness/thesaurus/narrower (accessed September 23, 2026). |
| Harvard | Smart Define 2016, doubtfulness thesaurus, Smart Define, viewed 23 September, 2026, <https://smartdefine.org/doubtfulness/thesaurus/narrower>. |
| MLA | Smart Define. "doubtfulness thesaurus" 29 February 2016. Web. 23 September 2026. <https://smartdefine.org/doubtfulness/thesaurus/narrower> |