What are the Strategic Approaches that can give a firm sustainable competitive advantage?

Igor Ansoff's approach- provides strategic approaches based on product & market information for instance New products Vs Existing markets, Existing products Vs Existing markets, Existing products Vs New markets, New products Vs New markets.

Glueck's approach- Stability, Expansion, Retrenchment strategy and combination strategy.

Michael Porter's approach- Overall cost leadership, Differenciation and Focus strategy.

Kotler's approach- Market leader's strategies, Marke follower's strategies, Market challanger's strategies and Market nicher's strategies