Entry Barriers and Entry Strategies, Journal of Strategic Management Education
Potential entrants may discern three types of entry barriers that result from three possible competitive advantages of incumbent firms: cost advantage, differentiation advantage, and transaction advantage. Competitive advantages tend to be temporary, due to technological change and changes in customer demand, so that entrants can devise various types of competitive strategies to overcome perceived barriers to entry.
Spulber, Daniel. 2003. Entry Barriers and Entry Strategies. Journal of Strategic Management Education. 1(1): 55-80.