| APA | Smart Define. (2015). vacuum-tube hearing aid thesaurus. Retrieved October 1, 2026, from https://smartdefine.org/vacuum-tube_hearing_aid/thesaurus/synonyms |
| Chicago | Smart Define. 2015. "vacuum-tube hearing aid thesaurus" https://smartdefine.org/vacuum-tube_hearing_aid/thesaurus/synonyms (accessed October 1, 2026). |
| Harvard | Smart Define 2015, vacuum-tube hearing aid thesaurus, Smart Define, viewed 1 October, 2026, <https://smartdefine.org/vacuum-tube_hearing_aid/thesaurus/synonyms>. |
| MLA | Smart Define. "vacuum-tube hearing aid thesaurus" 10 April 2015. Web. 1 October 2026. <https://smartdefine.org/vacuum-tube_hearing_aid/thesaurus/synonyms> |