Levi visited over 130 schools to talk about his experiences in Auschwitz. He vigorously repudiated revisionist attitudes in German historiography that emerged in the Historikerstreit led by the works of people like Andreas Hillgruber and Ernst Nolte, who drew parallels between Nazism and Stalinism. Levi rejected the idea that the labor camp system depicted in Aleksandr Solzhenitsyn's "The Gulag Archipelago" and that of the Nazi (; see Nazi concentration camps) were comparable. The death rate in Stalin's gulags was 30% at worst, he wrote, while in the extermination camps he estimated it to be 90–98%.