Sikkim
India's annexation of Sikkim in 1975 was rejected by China at the time. The Sino-Indian Memorandum of 2003 was hailed as a de facto Chinese acceptance of the annexation. China published a map showing Sikkim as a part of India and the Foreign Ministry deleted it from the list of China's "counties and regions". However, the Sikkim-China border continues to be the subject of dispute and military activity.
Read more about this topic: South Tibet Dispute