 Complete the following phrase:  In 1955, four athletes, led by Xu Jing, went to Soviet Transcaucasia to study mountaineering with an invitation from the Soviet Union. In 1957, six mountaineers, including Shi Zhanchun and Liu Lianman, summited Minya Konka, setting a domestic mountaineering record. The same year, the Soviet Union suggested to the Chinese Government that a Sino-Soviet joint climbing team should be formed for Mount Everest. The expedition was originally set for May 1959, but had to be postponed to 1960 due to the 