Reichheld, F. (2006). The Ultimate Question. HBR Press.
Lua i Stíl Chicago (17ú heag.)Reichheld, Fred. The Ultimate Question. Boston: HBR Press, 2006.
Lua MLA (9ú heag.)Reichheld, Fred. The Ultimate Question. HBR Press, 2006.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.