"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.