1991 Sino-Soviet Border Agreement
The 1991 Sino–Soviet Border Agreement was a treaty signed between China and the Soviet Union. The treaty was witnessed by General Secretary of the Chinese Communist Party Jiang Zemin and General Secretary of the Communist Party of the Soviet Union Mikhail Gorbachev on May 16, 1991, during Jiang's official visit to the Soviet Union.
Source: Wikipedia — 1991 Sino-Soviet Border Agreement (CC BY-SA 4.0)