Sino-Portuguese Joint Declaration
The Joint Declaration on the Question of Macau, or Sino-Portuguese Joint Declaration, was a treaty between Portugal and the People's Republic of China over the status of Macau. The full name of the treaty is Joint Declaration of the Government of the Portuguese Republic and the Government of the People's Republic of China on the question of Macau.
Source: Wikipedia — Sino-Portuguese Joint Declaration (CC BY-SA 4.0)