Austrian President Heinz Fischer signs the book of condolences for the late Polish President Lech Kaczynski and the victims of Saturday's plane crash, at the Polish embassy in Vienna April 12, 2010. Russian and Polish investigators struggled on Monday to identify the remains of nearly 100 people killed in a weekend plane crash in which Poland's president and many other top officials perished. REUTERS/HBF/Dragan Tatic (AUSTRIA - Tags: POLITICS OBITUARY)