'Yahad-In Unum's research so far indicates that 1 million Jews "from Poland to Ossetia" were shot dead and laid in mass graves, many of whom were unaccounted for in previous Holocaust research.More here http://www.timesofisrael.com/exposing-a-hidden-shoah-one-mass-grave-at-a-time
"A whole part of the genocide has not been declared," Desbois told The Times of Israel. "The challenge is to collect the maximum amount of evidence about the killing of the Jews in these countries and find out about the mass graves. Tomorrow the witnesses will disappear and the deniers will overreact, saying that the Jews falsified the story."'
A fascinating and distressing story. Not one that the Holocaust deniers will accept of course.