Reichheld, F. (2006). The Ultimate Question. HBR Press.
Cita Chicago (17th ed.)Reichheld, Fred. The Ultimate Question. Boston: HBR Press, 2006.
Cita MLA (9th ed.)Reichheld, Fred. The Ultimate Question. HBR Press, 2006.
Atenció: Aquestes cites poden no estar 100% correctes.