Sewell, C. (2002). Customers for Life (1st.). Crown Business.
Cita Chicago (17th ed.)Sewell, Carl. Customers for Life. 1st. Crown Business, 2002.
Cita MLA (9th ed.)Sewell, Carl. Customers for Life. 1st. Crown Business, 2002.
Atenció: Aquestes cites poden no estar 100% correctes.