sentences:  Shortly before the outbreak of World War II Sokolov was appointed to lead a Soviet field research company in China.After two years of field work in Tian Shan, the Turpan Depression and Tarim Basin (1941–1943) he returned to Soviet Central Asia to search for petroleum deposits on the northern side of Tian Shan.In 1945 he returned to Leningrad to complete his postgraduate thesis on Chaetetida, based on his pre-war studies.