When looking at Porter's works as a whole Group of answer choices Porter's first article (1985) is really about the value chain Porter's second article (1996) is about combining the concepts of the value chain, i.e. operational efficiency, with differentiation/strategic positioning Porter's 3rd article (2008) is about expanding the five forces model Porter refines his thinking in the (1996) article to include thinking about constraints and strategic choices All of the above