Lucas, R. W. (2009). Customer Service (4th.). McGraw Hill.
Chicago Style aipamenaLucas, Robert W. Customer Service. 4th. New York: McGraw Hill, 2009.
MLA aipamenaLucas, Robert W. Customer Service. 4th. McGraw Hill, 2009.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.