COWELL DONALD W. (1984). MARKETING SERVICES. HEINEMANN.
Lua i Stíl Chicago (17ú heag.)COWELL DONALD W. MARKETING SERVICES. LONDON: HEINEMANN, 1984.
Lua MLA (9ú heag.)COWELL DONALD W. MARKETING SERVICES. HEINEMANN, 1984.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.