It is widely agreed that Shangshu was the earliest collection of essays in China, covering important historical documents of the Shang (17th century-11th century B.C.) and Zhou (1066 -256 B.C.) dynasties.

"It was the most important evidence and material to research the ancient part of China's history," Li said.

According to him, Shangshu included more than 100 articles before the Qin Dynasty (221-206 B.C.), but after the Emperor Qinshihuang ordered the burning of all historical texts except classics of the Legist School, one of the major philosophic and political thoughts in China at that time, most of the articles of the Shangshu were lost.

Shangshu has long been considered to be an ancient classic on politics and philosophy in China. It served as the textbook of Chinese emperors and was one of the required readings of noble family members in the past. Many institutions, political thoughts, cultural beliefs and ideologies of China were written in it.

To the surprise of all the scholars who were invited by Tsinghua to study the donated bamboo strips, many articles in the Shangshu found in the Tsinghua collection are new to them, which means that these articles were written before the book-burning incident in the Qin Dynasty and escaped that cultural catastrophe.

"Thus, the significance of these unseen articles written on these bamboo strips is immeasurable to the study of the early part of the history of China ," Li said.

Another important content of these strips is a historic book in the style of annals. According to Li, based on the research of archaeologists and historians, the book recorded the history starting from the early period of the West Zhou Dynasty (1046-771 B.C.) to the early days of the Warring States Period. It has some new contents compared with the famous historic classics that have been passed down, such as Chunqiu, or the Spring and Autumn Annals, the earliest chronicle in China that covers the history from 722 B.C. to 481 B.C., and Shiji, or the Historical Records, China's oldest history book.

"Actually our study of these bamboo strips is in the primary stage. We have known that they also include some other important historic books or documents, which have never been seen for over 2,000 years," Li said.

Li said that experts guessed that these strips might come from ancient tombs, as most discoveries of ancient bamboo-strip documents in recent years were related with excavation of ancient tombs.

"We should thank the person who was buried in the tomb where these bamboo strips were unearthed," said Li, adding that he had left valuable documents behind and was perhaps a historian himself.

Li also pointed out the difficulties of studying the characters written on the strips. He said that the number of the characters written on these bamboo strips was estimated to exceed 10,000, and experts have not estimated when they will finish reading these ancient documents, as the written characters in the Warring States Period varied largely in different states. It was only after Emperor Qinshihuang united the major seven states at that time that China had a unified system of writing.

Difficult to preserve

When this batch of bamboo strips was brought to Tsinghua, they were wrapped with plastic film and sealed in canisters containing liquid. Some of the strips risked getting moldy, Li said.

Experts replaced the original liquid with distilled water, changing it every two or three days, and cleaned the remaining dirt on the strips painstakingly with soft brushes.

But how to further preserve these treasures in the future still needs to be answered.

"If the bamboo strips are preserved in a dry environment, it will affect the way they look, but if they are preserved in liquid, they will face the danger of getting moldy," Li said.

Xie Weihe, Vice President of Tsinghua University, said at the October press conference that the university would invite scholars and scientists either at home or abroad to participate in the study and protection of these cultural treasures.

He also said that Tsinghua University is planning to build a museum to show these treasures to the public.

The Warring States Period

The years between 476 B.C. and 221 B.C. are known as the Warring States Period. Many states had disappeared after the wars of the Chunqiu Period, or the Spring and Autumn Period (770-476 B.C.), bringing great social changes during the Warring States Period. Quite a number of schools of thought contended for dominance in the realm of intellect. The statesmen at that time were quick to pick up on these changes and pressed ahead with political reforms, which led to the historical trend of unification.

The Warring States Period can be divided into three stages. The first stage began in 476 B.C. and ended in 338 B.C. when King Zhou, the last king of the Shang Dynasty, was killed. During this period, many statesmen were eager to strengthen their states through reform, such as Li Kui in Wei, Wu Qi in Chu and Shang Yang in Qin. Qin's Prime Minister Shang Yang launched sweeping reforms, which included private ownership of and transactions in land, abolition of forced labor on farmers, and the division of the state into 31 counties which were supervised by officials directly appointed by the duke. Shang Yang's reform had a great deal to do with Qin's emergence as the most powerful state in the late Warring States Period. This stage was a comparatively stable period.

The second stage began in 338 B.C. and ended in 288 B.C. During this period fierce fighting persisted among the seven powers as each tried to annex its neighbor. In 288 B.C., Qi and Qin became the Western Empire and Eastern Empire. The wars escalated. In 284 B.C., Qin and the five other states united and launched a war against Qi, the strongest power at that time.

Agriculture, industry and economy developed quickly during the Warring States Period. The increasing popularity of iron tools marked a revolutionary innovation in tools and the development of increased productivity.

The third stage was from 284 B.C. to 221 B.C. In 221 B.C., the State of Qin unified the entire country after conquering its six rival states, ending the turbulent Warring States Period.