| APA | Smart Define. (2011). douglas fir thesaurus. Retrieved September 24, 2026, from https://smartdefine.org/douglas_fir/thesaurus/narrower |
| Chicago | Smart Define. 2011. "douglas fir thesaurus" https://smartdefine.org/douglas_fir/thesaurus/narrower (accessed September 24, 2026). |
| Harvard | Smart Define 2011, douglas fir thesaurus, Smart Define, viewed 24 September, 2026, <https://smartdefine.org/douglas_fir/thesaurus/narrower>. |
| MLA | Smart Define. "douglas fir thesaurus" 26 April 2011. Web. 24 September 2026. <https://smartdefine.org/douglas_fir/thesaurus/narrower> |