What is "cangjiepian"

The Cangjiepian, also known as the Three Chapters (, Sancang), was a BCE Chinese primer and a prototype for Chinese dictionaries. Li Si, Chancellor of the Qin dynasty (221-206 BCE), compiled it for the purpose of reforming written Chinese into the new orthographic standard Small Seal Script. Beginning in the Han dynasty (206 BCE-221 CE), many scholars and lexicographers expanded and annotated the Cangjiepian. By the end of the Tang dynasty (618-907), it had become a lost work, but in 1977, archeologists discovered a cache of (c. 165 BCE) texts written on bamboo strips, including fragments of the Cangjiepian.