Mark Rudd, former chairman of the Columbia chapter of Students for a Democratic Society and co-founder of the Weather Underground discusses and signs his memoir Underground (Harper, $13.99), now released in paperback.Rudd and his friends sought to end war, racism, and injustice - by any means necessary.  In this gripping narrative, Rudd speaks out about this tumultuous period, the role he played in its crucial events, and its aftermath, revealing the drama and tension as well as the naivete of young activists.From 1980 to 2006 Rudd was a math instructor at CNM, and a perennial organizer and nonviolent activist locally on issues of Native American land rights, nuclear, US military interventions, Palestine solidarity, unionization, environmental justice, and war and militarization.