Sewell Carl. (1990). Customers for Life: How to turn that one-time buyer into a lifetime customer. Pocket Books Publishing.
Lua i Stíl Chicago (17ú heag.)Sewell Carl. Customers for Life: How to Turn That One-time Buyer into a Lifetime Customer. NewYok: Pocket Books Publishing, 1990.
Lua MLA (9ú heag.)Sewell Carl. Customers for Life: How to Turn That One-time Buyer into a Lifetime Customer. Pocket Books Publishing, 1990.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.