" There is yet another bit of illogic on which deniers depend. They demand to be shown the one specific piece of evidence that would prove to them there was a Holocaust: Hitler’s written order authorizing the murder of all of Europe’s Jews. In all likelihood, Hitler realized the folly of affixing his signature to such an order, which, had it become public, many might not have accepted. More important, historians are not troubled by the absence of such a document. They never rest their conclusions on one document, particularly in this instance, when the Third Reich left a vast cache of evidence attesting to a government-directed program whose goal was the annihilation of the Jewish people. Deniers, of course, will insist that “the Jews” have forged these documents. But if that were the case, why didn’t the Jews also forge the all-important document from Hitler himself? "

― Deborah E. Lipstadt , Antisemitism: Here and Now