The report by the Ministry of Revenue in 1869 detailing Da Nang authorities' allocation of rice to help 540 people from China's Fujian Province who got stranded on Truong Sa. (Photo: VnExpress/Nguyen Dong)

The documents show the establishment and exercising of Vietnamese sovereignty over the Hoang Sa (Paracel) and Truong Sa (Spratly) islands by the Nguyen Dynasty, which ruled from 1802 to 1945.

They include report, made public for the first time, by the Ministry of Revenue in 1869 detailing Da Nang authorities' allocation of rice to help hundreds of people from China's Fujian Province who got stranded on Truong Sa.Other documents include a map of Hoang Sa Islands published by the French Navy in 1885 and reprinted in 1940 based on a survey conducted by the Germans in 1881-83 and a research paper on the battles Vietnamese naval forces had fought to defend the country.

There are also paintings of Truong Sa Islands and propaganda posters promoting Vietnam's sovereignty over the islands, and a map of Tourane, French name for Da Nang at the time, published by the Indochina Geographical Department in November 1898 that clearly shows Hoang Sa Islands as part of the city.