Sewell, C. (2002). Customers for Life (1st.). Crown Business.
Lua i Stíl Chicago (17ú heag.)Sewell, Carl. Customers for Life. 1st. Crown Business, 2002.
Lua MLA (9ú heag.)Sewell, Carl. Customers for Life. 1st. Crown Business, 2002.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.