SCHIFFMAN STEPHAN. (2005). 25 SALES HABITS OF HIGHLY SUCCESSFUL SALESPEOPLE. ADAMS MEDIA CORPORATION.
Chicago Style aipamenaSCHIFFMAN STEPHAN. 25 SALES HABITS OF HIGHLY SUCCESSFUL SALESPEOPLE. MASSACHUETTS: ADAMS MEDIA CORPORATION, 2005.
MLA aipamenaSCHIFFMAN STEPHAN. 25 SALES HABITS OF HIGHLY SUCCESSFUL SALESPEOPLE. ADAMS MEDIA CORPORATION, 2005.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.