July 2012 (UTC)

In the case of Poland, there were censuse both before and after the War, and religious affiliation was assigned at birth, and very hard to subsequently change [birth registration was in the hands of religious bodies].  In any event, the sheer number of eye-witnesses to what went on, Home Army {resistance] intelligence reports, and the testimonies of Jewish, Polish and other collaborators as well as Germans in post-war trials, along with thorough German documentary evidence, made the sad task easier.
One only had to look around to see absence evereywhere, seems to be the survivors common testimony. 86.12.129.2  11:22, 15