  While manuscript versions inform textual criticism of the Laozi, stone inscriptions provide further collaborating support. Over twenty steles, mainly of Tang and Song origins, are available to textual critics, although some are in poor condition (Yan 1957). Students of the Laozi today can work with several Chinese and Japanese studies that make use of a large number of manuscript versions and stone inscriptions (notably Ma 1965, Jiang 1980, Zhu 1980, and Shima 1973). Boltz (1993) offers an excellent introduction to the manuscript traditions of the Laozi. Wagner (2003) attempts to reconstruct the original face of Wang Bi’s Laozi (cf. Lou 1980 and Lynn 1999). A major contribution to Laozi studies in Chinese is Liu Xiaogan 2006, which compares the Guodian, Mawangdui, Fu Yi, Wang Bi, and Heshanggong versions of the Laozi and provides detailed textual and interpretive analysis for each chapter. In an article in English, Liu (2003) sets out some of his main findings.