The document discusses two main approaches to developing sustainable competitive advantage (SCA): the industrial organization (I/O) approach and the resource-based view (RBV) approach. The I/O approach argues that external industry factors are most important, while the RBV contends that internal resources are key. Effective strategy requires understanding both external and internal factors. Core competencies that are rare, valuable, and difficult to imitate can provide SCA if they allow access to markets and delivery of customer value that competitors cannot duplicate.