Không rõ. (2001). About Customers: Gathering Information. Youth PublishingHouse.
Παραπομπή Chicago StyleKhông rõ. About Customers: Gathering Information. Youth PublishingHouse, 2001.
Παραπομπή MLAKhông rõ. About Customers: Gathering Information. Youth PublishingHouse, 2001.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.