^Chacarbaghi; Lynch, Competitive Advantage: Creating and Sustaining Superior Performance by Michael E. Porter 1980: 45, 1999
^A firm is said to have a competitive advantage when it is implementing a value creating strategy not simultaneously being implemented by any current or potential player
^Clulow, Val; Gerstman, Julie; Barry, Carol. The resource-based view and sustainable competitive advantage: the case of a financial services firm. Journal of European Industrial Training. 1 January 2003, 27 (5): 220–232. doi:10.1108/03090590310469605.