Sewell Carl. (1990). Customers for Life: How to turn that one-time buyer into a lifetime customer. Pocket Books Publishing.
Чикаго-гийн эшлэл (17 дахь хэвлэлт)Sewell Carl. Customers for Life: How to Turn That One-time Buyer into a Lifetime Customer. NewYok: Pocket Books Publishing, 1990.
MLA -ийн эшлэл (9 дэх хэвлэлт)Sewell Carl. Customers for Life: How to Turn That One-time Buyer into a Lifetime Customer. Pocket Books Publishing, 1990.
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