Barrera, R. (2005). Overpromise and overdeliver: The secrets of unshakable customer loyality. Penguin.
Chicago Edition CitationBarrera, Rick. Overpromise and Overdeliver: The Secrets of Unshakable Customer Loyality. New Delhi: Penguin, 2005.
MLA Edition CitationBarrera, Rick. Overpromise and Overdeliver: The Secrets of Unshakable Customer Loyality. Penguin, 2005.
Advarsel: Disse citationer er muligvist ikke 100% nøjagtige.