How are ancient books handed down?

Sikuquanshu is an important edition. Many of them are collected by folk scholars and academies, but there are also archaeological excavations. When versions are copied and printed, there are often some differences. At this time, it is necessary to trace back to the oldest version, such as Laozi's Tao Te Ching, which has been annotated by many people in past dynasties, but there are various explanations for the length of time. Laozi A and B recently excavated by the archaeological community are ancient in the Warring States period, which are closer to the original text and more reliable. Similarly, so are all kinds of other books.