The Jews that were in the camps documented the groups of people by names and relatives so that the other family members would know what happened to their loved ones.... My daughter went to 2 of the death camps in Poland..... She went with a Polish family that she was visiting in 2003. It had a big impact on her. And it was not just the Jews although they were the majority... The Gypsies, the Polish people... You can bet your last can of beer that it is all very well documented as the Germans themselves kept meticulous records and only some were destroyed.
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