Coba jelasin Rujukan dari United Parcel Service dalam bahasa melayu dong

Brewster, Mike and Frederick Dalzell. Driving Change: The UPS Approach to Business (2007) excerpt and text search

Thomas L. Friedman, "Insourcing," in The World Is Flat: A Brief History of the Twenty-First Century, New York: Farrar, Straus and Giroux, updated and expanded, 2006, pp. 167–176.

Minchin, Timothy J., "Shutting Down 'Big Brown': Reassessing the 1997 UPS Strike and the Fate of American Labor," Labor History, 53 (Nov. 2012), 541–60.

Niemann, Greg. Big Brown: The Untold Story of UPS John Wiley & Sons, 2007

Allen, Joe, The Package King: A Rank and File History of United Parcel Service