This is the accepted time scheme in China. The dates are the Western equivalents of the most widely current Chinese computation, which is known to be incorrect or haphazard from the eighth century b.c. back. The periods given for the dynasties are chronological formulas rather than the exact expression of political realities. For a discussion of the materials of Chinese historiography, see Charles S. Gardner, Chinese Traditional Historiography, Cambridge, 1938. For an excellent short summary of Chinese history, see the "Historical Sketch" by Lei Hai-tsung in The Chinese Year Book, 1936-1937, Shanghai. Chronologies are to be found in the major Chinese-English dictionaries, and—among many others—in Leon Wieger, S. J., La Chine À travers les Âges, Hsien-hsien, 1920, where they are accompanied by a great deal of the old-style, uncritical, but nevertheless informative, Chinese scholarship.