Supporters of late Poland's President Lech Kaczynski gather to protest the results of a Russian investigation into the fatal plane crash that killed all 96 people on board including the Polish President one year ago, in front of the Russian embassy in Warsaw April 9, 2011. Fierce arguments have erupted between the two countries over the cause of the crash, which a Russian report in January blamed on the Polish pilots and absolved its own ground control of any responsibility. REUTERS/Kacper Pempel (POLAND - Tags: CIVIL UNREST POLITICS)