“Silkworm Head & Goose Tail” refer to the start and ending of horizontal strokes typically written in Li Shu. When one has learned this, the other principles of Li Shu are relatively easy as explained in the following videos.
http://www.art-virtue.com/styles/li/index.htm
Chinese calligraphy Clerical Style “Li Shu”
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Duration : 0:5:34