A worker digs graves at a memorial centre for Srebrenica Massacre victims in Potocari July 5, 2015. Tens of thousands of family members, foreign dignitaries and guests are expected to attend a ceremony in Srebrenica on July 11 marking the 20th anniversary of the massacre in which Bosnian Serb forces commanded by Ratko Mladic killed up to 8,000 Muslim men and boys. Nearly 136 identified victims will be buried at a memorial cemetery during the ceremony, their bodies found in some 60 mass graves around the town. REUTERS/Dado Ruvic