FREEMANTLE, D. (1992). Incredible Customer Service. McGraw-Hill.
Chicago Style aipamenaFREEMANTLE, David. Incredible Customer Service. McGraw-Hill, 1992.
MLA aipamenaFREEMANTLE, David. Incredible Customer Service. McGraw-Hill, 1992.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.