Rank	Country	Date
1	USSR	April 12, 1961
2	United States	February 20, 1962
3	Czechoslovakia	March 2, 1978
4	Poland	June 27, 1978
5	East Germany	August 26, 1978
6	Bulgaria	April 10, 1979
7	Hungary	May 26, 1980
8	Vietnam	July 23, 1980
9	Cuba	September 18, 1980
10	Mongolia	March 22, 1981

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