The more than 50 volumes of photographed archives were made public on Thursday as the Chinese Academy of Social Sciences showcased its latest progress in the research about the history of the South China Sea.
The documents were collected by Professor Tang Yi with the Taiwan-based National Chengchi University.
The professor has spent decades in the research over border demarcation issues in Chinese history.
He said what he presented shows China's sovereignty over the South China Sea is a historical fact.
"The map published by the then Nationalist government in 1935 shows the Chinese territory in the South China Sea looked like this. And in the next year, we took over the Xisha and Nansha islands from Japan and claimed territorial rights over the area. These islands belong to China, it's inarguable."
Wang Jianyong with the Institute of Modern History under the CASS says the documents bring to light many untold truths.
"We see many of these documents for the first time. They tell us that the governments of America, Japan and the Philippines used to accept China's territorial claim over the area. Their flights used to request weather service from Taiwan when flying over the area. At least, in a certain period, they had no problems with China's jurisdiction over South China Sea."
Li Guoqiang with CASS' Institute of Chinese Borderland Studies suggests when a country claims rights over an area of land or sea, it should prove it's the first to reach, to develop and to set up administration there.
He adds that Chinese activities in the South China Sea date back 2,200 years, during the Qin Dynasty.
"Chinese historians acknowledge the presence of the countries bordering the South China Sea and their ancestors' activities in the area. But they can't be compared with China that had discovered, developed and administrated the waters since ancient times. The historical facts they piece together can't change the fact that it's Chinese territory."
It's widely suggested that the South China Sea became an issue in the 1960s and '70s, when some countries in the region began to occupy some of the islands under China's jurisdiction.
For CRI, this is Huang Yue.
