上古音
The first complete reconstruction of Old Chinese was produced by the Swedish linguist Bernhard Karlgren in a dictionary of Middle and Old Chinese, the "Grammata Serica" (1940), revised in 1957 as the "Grammata Serica Recensa" (GSR). Although Karlgren's Old Chinese reconstructions have been superseded, his comprehensive dictionary remains a valuable reference for students of Old Chinese, and characters are routinely identified by their GSR position.