2010/04/12 Headlines: Afghan Civilians Slain in US Attack on Passenger Bus; Clinton Touts US Nuclear Dominance Ahead of DC Summit; Justice Stevens Announces Retirement from Supreme Court; Obama Pick Withdraws Nomination for Legal Office; Gates Defends US Attack on Iraqi Civilians in Leaked Video; W. Va. Toll Hits 29 as 4 Missing Miners Found Dead; Poland Mourns Death of President, Top Officials in Russia Plane Crash; Thai Protesters Killed in Police Attack; Palestinians Face Mass Deportations, Jailings under New Israeli Order; Kazakhstan Grants US Overflight Rights for Afghan War; US Cancels Climate Aid to Bolivia, Ecuador over Copenhagen Opposition