Playing cards may have been invented during the Tang dynasty around the 9th century AD as a result of the usage of woodblock printing technology. The earliest known text containing a possible reference to card games is a 9th-century text known as the "Collection of Miscellanea at Duyang", written by Tang dynasty writer Su E. It describes Princess Tongchang, daughter of Emperor Yizong of Tang, playing the "leaf game" in 868 with members of the Wei clan, the family of the princess's husband. The first known book on the "leaf" game was called the "Yezi Gexi" and allegedly written by a Tang woman. It received commentary by writers of subsequent dynasties. The Song dynasty (960–1279) scholar Ouyang Xiu (1007–1072) asserts that the "leaf" game existed at least since the mid-Tang dynasty and associated its invention with the development of printed sheets as a writing medium. However, Ouyang also claims that the "leaves" were pages of a book used in a board game played with dice, and that the rules of the game were lost by 1067.