About 40 percent of the documents held by the State Archive Administration have now been opened up to public scrutiny, the head of the administration said on Tuesday.

A staff member of the State Archives Administration gives an introduction to reporters from home and abroad on Tuesday.

Yang Dongquan said the archives in downtown Beijing contain more than 100 million pages and many of them are available to the public.

People wanting to look at documents need to show their identity cards and research achievements in a related field along with letters of introduction from their employers if they want to see the declassified materials.

"Files of importance to national security and defense, foreign affairs, religion and personal privacy are not suitable to be opened up," Yang told reporters during a government-organized visit, adding that whether materials are made public depends more on the contents of the documents than their age.

According to Chinese law, the majority of secret documents can be seen by the public 30 years after they are classified.

Documents displayed during the tour included a copy of the Party's first resolution, which was passed in July 1921, when the first Communist Party of China (CPC) National Congress was convened to declare the Party's formal establishment, said Li Minghua, the administration's deputy head.

Li also showed a copy of a letter written by the 14th Dalai Lama to Chairman Mao in October 1951.

The 14th Dalai Lama said in the letter that "the local government of Tibet as well as the Tibetan monks and laymen unanimously support this agreement, and will actively assist the People's Liberation Army in Tibet to consolidate national defense, drive imperialist influences out of Tibet and safeguard the unification of the territory and the sovereignty of the motherland".

Yang said the primary function of archiving is to offer reference and experience to the current State leaders.

"With the help of old materials, officials can compare the past with current events to enhance their governance skills," he said.

He also said the materials are useful in recording a faithful history, safeguarding the unification of territory and informing younger generations.

He said the documents kept in the archives will be made available to a wider section of the public.

The State Achieves Administration, which was founded in 1954, is responsible for collecting, arranging, preserving and providing access to documents with long-term value.

All documents held by the administration are the archives of the CPC and the People's Republic of China, while materials from governments from earlier than 1949 are in the country's two historical archives.