executed. Many Americans who had emigrated to the Soviet Union during the worst of the Great Depression were executed, while others were sent to prison camps or gulags. Concurrent with the purges, efforts were made to rewrite the history in Soviet textbooks and other propaganda materials. Notable people executed by NKVD were removed from the texts and photographs as though they never existed. Gradually, the history of the revolution was transformed into a story about just two key characters, i.e. Lenin and Stalin. In light of revelations from Soviet archives, historians now estimate that nearly 700,000 people (353,074 in 1937 and 328,612 in 1938) were executed in the course of the terror, with the great mass of victims merely "ordinary" Soviet citizens: workers, peasants, homemakers, teachers, priests, musicians, soldiers, pensioners, ballerinas, and beggars. Many of the executed were interred in mass graves, with some significant killing and burial sites being Bykivnia, Kurapaty, and Butovo. Some Western experts believe the evidence released from the Soviet archives is understated, incomplete or unreliable. Conversely, historian Stephen G. Wheatcroft, who spent a good portion of his academic career researching the archives, contends that, prior to the collapse of the Soviet Union and the opening of the archives for historical research, "our understanding of the scale and the nature of Soviet repression has been extremely poor" and that some specialists who wish to maintain earlier high estimates of the Stalinist death toll are "finding it difficult to adapt to the new circumstances when the archives are open and when there are plenty of irrefutable data" and instead "hang on to their old Sovietological methods with round-about calculations based on odd statements from emigres and other informants who are supposed to have superior knowledge." Stalin personally signed 357 proscription lists in 1937 and 1938 that condemned to execute some 40,000 people, about 90% of whom are confirmed to have been shot. While reviewing one such list, he reportedly muttered to no one in particular: "Who's going to remember all this riff-raff in ten or twenty years time? No one. Who remembers the names now of the boyars Ivan the Terrible got rid of? No one." In addition, Stalin dispatched a contingent of NKVD operatives to Mongolia, established a Mongolian version of the NKVD troika, and unleashed a bloody purge in which tens of thousands were executed as "Japanese spies", as Mongolian ruler Khorloogiin Choibalsan closely followed