Press, pp.49-53 Argyres, N., & McGahan, A. M., 2002, "Introduction: Michael Porter" Competitive Strategy, Academy of Management Executive , vol. 16, No. 2, pp.41-42   Arthur , S., & Sheffrin, S.M., 2003, Economics: Principles in action . Upper Saddle River, New Jersey: Pearson Prentice Hall. p. 30-39   Co-operative Financial Services, 2009;