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In page Bamboo:

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Bamboo was in widespread use in early China as a medium for written documents. The earliest surviving examples of such documents, written in ink on string-bound bundles of bamboo strips (or "slips"), date from the fifth century BC during the Warring States period. References in earlier texts surviving on other media indicate some precursor of these Warring States period bamboo slips was used as early as the late Shang period (from about 1250 BC).[citation needed]