  The division into 81 chapters reflects numerological interest and is associated particularly with the Heshanggong version, which also carries chapter titles. It was not universally accepted until much later, perhaps the Tang period, when the text was standardized under the patronage of Emperor Xuanzong (r. 712–756). Traditional sources report that some versions were divided into 64, 68, or 72 chapters; and some did not have chapter divisions (Henricks 1982).