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Google is the subject of major antitrust investigations in the United States and Europe. In the United States, regulators are expected to announce a decision within days to sue or settle, and under what terms. The European decision will come soon as well. Much has changed over the years, but two lawyers who helped build the case against Microsoft are playing important roles once again. But this time, Gary L. Reback and Susan A. Creighton are on opposite sides. The two lawyers, and the positions they have taken, point to some striking similarities yet also significant differences between the two high-stakes investigations — and why the pursuit of Google has proved challenging for antitrust officials.