but they also did not want to pay too much attention to this issue in order to avoid stirring national sentiment. In 1942, Stepan Sosnovy, an agronomist in Kharkiv, published a comprehensive statistical research on the number of Holodomor casualties, based on documents from Soviet archives. In the post-war period, the Ukrainian diaspora disseminated information about the Holodomor in Europe and North America. At first, the public attitude was rather cautious, as the information came from people who had lived in the occupied territories, but it gradually changed in the 1950s. Scientific study of the Holodomor, based on the growing number of memoirs published by survivors, began in the 1950s. Death toll The Soviet Union long denied that the famine had taken place. The NKVD (and later KGB) controlled the archives for the Holodomor period and made relevant records available very slowly. The exact number of the victims remains unknown and is probably impossible to estimate even within a margin of error of a hundred thousand. However, by the end of 1933, millions of people had starved to death or otherwise died unnaturally in the Soviet republics. In 2001, based on a range of official demographic data, historian Stephen G. Wheatcroft noted that official death statistics for this period were systematically repressed and showed that many deaths were un-registered. Estimates vary in their coverage, with some using the 1933 Ukraine borders, some of the current borders, and some counting ethnic Ukrainians. Some extrapolate on the basis of deaths in a given area, while others use archival data. Some historians question the accuracy of Soviet censuses, as they may reflect Soviet propaganda. Other estimates come from recorded discussions between world leaders. In an August 1942 conversation, Stalin gave Winston Churchill his estimates of the number of "kulaks" who were repressed for resisting collectivisation as 10 million, in all of the Soviet Union, rather than only in Ukraine. When using this number, Stalin implied that it included not only those who lost their lives but also those who were forcibly deported. There are variations in opinion as to whether deaths in Gulag labour camps should be counted or only those who starved to death at home. Estimates before archival opening varied widely such as: 2.5 million (Volodymyr Kubiyovych); 4.8 million (Vasyl Hryshko); and 5 million (Robert Conquest). In the 1980s, dissident demographer and historian Alexander P. Babyonyshev (writing as Sergei Maksudov) estimated