| APA | Smart Define. (2013). electron tube thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/electron_tube/thesaurus/narrower |
| Chicago | Smart Define. 2013. "electron tube thesaurus" https://smartdefine.org/electron_tube/thesaurus/narrower (accessed September 26, 2026). |
| Harvard | Smart Define 2013, electron tube thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/electron_tube/thesaurus/narrower>. |
| MLA | Smart Define. "electron tube thesaurus" 19 May 2013. Web. 26 September 2026. <https://smartdefine.org/electron_tube/thesaurus/narrower> |