Warson, R. (1976). Commerce. Hodders & Stoughton.
Lua i Stíl Chicago (17ú heag.)Warson, Ronald. Commerce. London: Hodders & Stoughton, 1976.
Lua MLA (9ú heag.)Warson, Ronald. Commerce. Hodders & Stoughton, 1976.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.