Dr. Robert Rozett, director of the Yad Vashem Libraries, last week sent an email to Amazon CEO Jeff Bezos, requesting that he immediately remove the books from the sites.

“It has been clear for many years now that Holocaust denial literature is freely available for purchase over Amazon. Many of the items appear with glowing readers’ reviews and recommendations for further reading in the same vein,” Rozett wrote in the letter, the Jerusalem Post first reported.

“Once again, given the presence of anti-Semitism around the globe, which has become more prevalent in recent years, we strongly urge you to remove books that deny, distort and trivialize the Holocaust from your store,” the letter said.

Amazon has removed books that deny the Holocaust from online stores in countries where Holocaust denial is illegal, but they remain available in the United States and the United Kingdom.

The British newspaper The Independent reported earlier this month that the books were removed in some countries, including Italy, France and Germany, after Amazon was contacted about the sale of such books by The Sunday Times of London.

Among the books still available on Amazon’s U.S. and U.K. online stores are “Did Six Million Really Die?” by Richard Harwood; “The Six Million: Fact or Fiction?,” and “The Myth of the Extermination of the Jews.”