A book about the notes Chinese fishermen kept to guide them in navigating the South China Sea was released in Hainan province on Friday.

The book, called South China Sea Genglubu and issued by Hainan Publishing House, tells the story of Genglubu, books Chinese fishermen used to keep notes about the routes they sailed in the South China Sea.

The notes, with information on the ocean currents and islands, were important to Chinese seamen in a time when there was no modern positioning technology.

Twenty-four Genglubu transcripts have been found, according to the book, giving details on more than 200 routes in the South China Sea and naming 136 islands.

Wu Shaoyuan, assistant researcher of the National Institute for South China Sea Studies, said Genglubu provide important evidence supporting China's claim of historic rights in the South China Sea.

Zou Ligang, a law professor at Hainan University, said the release of the book at this time shows the Chinese people's opposition to the arbitration case filed by the Philippines regarding China and the South China Sea.

On Thursday, the day before the book was published, another nearly 70-year-old piece of evidence for China's sovereignty over the South China Sea islands was donated to the National South China Sea Museum, which is under construction.

The book called Nan Hai Zhu Dao Di Li Zhi Lue, or "A Brief Record of the Geography of the South China Sea Islands", was first published in 1947. It was compiled by a Chinese official who took part in retrieving the islands after the surrender of occupying Japanese troops.

The book records what was seen and heard during the official's retrieval mission from 1945 to 1947 and has a map of South China Sea islands.

According to Zhang Jianping, a member of the office that is planning the museum's construction, the map is the origin of the nine-dash map used by China to delineate the areas of its sovereignty in the South China Sea.

The museum is expected to open in 2017. Zhang said the book will be a key display item after the museum is opened.

Hainan Daily contributed to the story.

Contact the writers at liuxiaoli@chinadaily.com.cn and wangqingyun@chinadaily.com.cn