National treasure: Van Nhu Manh displays his family's precious book, Khai dong thuyet uoc, "The Rules of Teaching Children".

A map found in an ancient textbook on the history of the Nguyen dynasty confirms Viet Nam's sovereignty over the Hoang Sa (Paracel) and Truong Sa (Spratly) islands.

Van Nhu Manh told Sunday Viet Nam News that his family, who live in Son Hai Street in Sam Son Town, Thanh Hoa Province, found the map showing the two archipelagos as part of the country's territory on an ancient Vietnamese history and geography textbook. The 74-page book was written by Pham Phuc Trai, a mandarin at the Hue Royal Court.

First printed in 1881, the textbook was used in schools for hundreds of years and made use of four-word sentences to make it student-friendly, said Pham Thi Thuy Vinh, associate professor and deputy chief of the Institute of Han-Nom Studies.

Manh said his great-great grandfather, Van Dinh Bua, was a teacher in the Royal school in the Imperial Palace in Hue, so he has numerous books written in Han (Chinese script) and Nom in his collection.

Manh recalled that some time in 2012, when he repaired his house he discovered the book by chance.

"This made me curious enough to read the book. I was quite familiar with the Han and Nom scripts, so I realised that it was a textbook covering Viet Nam's astronomy, geography and topography," said Manh.

The "Our National Map" section, featured on page 9, showed the locations of all of Viet Nam's provinces and cities from Nam Quan, a northern border gate between Viet Nam and China, to Ha Tien in the South.

The Hoang Sa and Truong Sa island groups, as well as the country's official name and its mountains and rivers, are also on the map.

Manh then informed officials of the Thanh Hoa's Sam Son Town's Office of Culture, Sports and Tourism about the book.

Dam Thi Thai, deputy head of the office, confirmed this, saying, "Right after Manh informed us about the book, we and other town authorities followed him to his home and asked his family to carefully preserve the book and refrain from copying, printing and bringing it to other locations, since this is not allowed by authorities."

Town officials plan to bring the book to the Thanh Hoa provincial authorities for an appraisal of its real value to ensure long-term efforts are made for its preservation, according to Thai.

Vinh said the book was a rare and precious find that showed Viet Nam's sovereignty over the Hoang Sa and Truong Sa islands.

"The islands are clearly shown on this map. It proves that the Nguyen dynasty was aware of its sovereignty over these islands and the seas surrounding them. They placed the map in the textbook to educate future generations about this," said Vinh.

"We believe that the book is the earliest copy of its kind, so we can clearly see our seas and islands drawn on the map," he added.

Manh said his family was carefully preserving the book for use and reference by generations of Vietnamese.

"We wish scientists and researchers would carry out official research to confirm the book's real value," he added. "We also hope the State will place it in the national archive centre and announce its existence to the world to confirm Viet Nam's sovereignty over the Hoang Sa and Truong Sa archipelagos."