A man studies a laptop in a visitor's reading room at the archive of the Auschwitz-Birkenau Nazi concentration camp. It is estimated that between 1.1 and 1.5 million Jews, Poles, Roma and others were killed in Auschwitz-Birkenau during the Holocaust between 1940-1945. 27 January 2015 is the 70th anniversary of the liberation of Auschwitz-Birkenau.