| APA | Smart Define. (1970). primary source of energy thesaurus. Retrieved September 26, 2026, from https://smartdefine.org/primary_source_of_energy/thesaurus/narrower |
| Chicago | Smart Define. 1970. "primary source of energy thesaurus" https://smartdefine.org/primary_source_of_energy/thesaurus/narrower (accessed September 26, 2026). |
| Harvard | Smart Define 1970, primary source of energy thesaurus, Smart Define, viewed 26 September, 2026, <https://smartdefine.org/primary_source_of_energy/thesaurus/narrower>. |
| MLA | Smart Define. "primary source of energy thesaurus" 1 January 1970. Web. 26 September 2026. <https://smartdefine.org/primary_source_of_energy/thesaurus/narrower> |