Hill, H. C. (1928). Vocational civics. Ginn and Company.
Lua i Stíl Chicago (17ú heag.)Hill, Howard C. Vocational Civics. Boston ; London: Ginn and Company, 1928.
Lua MLA (8ú heag.)Hill, Howard C. Vocational Civics. Ginn and Company, 1928.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.