In this April 30, 1968 file photo, a student protester at Columbia University is forcibly removed from the campus by plainclothes New York City police after they entered buildings occupied by the students, and ejected those participating in the sit-ins. Fifty years ago, more than 700 protesters were arrested and more than 130 were injured when police retook the occupied buildings, during what was part of a year of global turmoil. (Photo by Dave Pickoff/AP Photo)
