His review of Piketty21 here. Summary and discussion in Why I am not persuaded by Thomas Piketty's argument. Another negative review discussed in The Economist "Capital" and its discontents. Some of these points are also discussed in Piketty's Huffington Post interview linked before. Possibly some of the points will be clarified in these discussions. It is time for my second reading of Piketty in the liht of these discussions. Check also Ten questions for Thomas Piketty.