钱学森于1991年退休,此后他安静地生活在北京,拒绝与西方人交谈。<ref>Peter Grier, "The forgotten 'spy' case of a rocket scientist"''The Christian Science Monitor'' Vol. 92 Issue 244, November 2000</ref> | 钱学森于1991年退休,此后他安静地生活在北京,拒绝与西方人交谈。<ref>Peter Grier, "The forgotten 'spy' case of a rocket scientist"''The Christian Science Monitor'' Vol. 92 Issue 244, November 2000</ref> |