Παραπομπή APA

Sviokla, J. J., & Shapiro, B. P. (1993). Keeping customers (11th ed.). HBR.

Παραπομπή Chicago Style

Sviokla, John J., και Benson P. Shapiro. Keeping Customers. 11th ed. HBR, 1993.

Παραπομπή MLA

Sviokla, John J., και Benson P. Shapiro. Keeping Customers. 11th ed. HBR, 1993.