Holocaust deniers have often quoted out of context Mayer's sentences in the book: "Sources for the study of the gas chambers are at once rare and unreliable". As the authors Michael Shermer and Alex Grobman have noted, the entire paragraph from which the sentence comes from states that the SS destroyed the majority of the documention relating to the operation of the gas chambers in the death camps, which is why Mayer feels that sources for the operation of the gas chambers are "rare" and "unreliable".