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FT Professional。业内人士推荐旺商聊官方下载作为进阶阅读
，详情可参考safew官方版本下载
Courtesy of Sharge。WPS下载最新地址对此有专业解读
The “Knocking on Wood” Wikipedia page mentions Roud’s conclusion, and this claim of a 19th century origin has circulated online as the final say on the matter. If you go back to the original, though, Roud’s proposal actually ends on an ambivalent note: “Before this theory [of 19th century origins] can be finally accepted, however, an examination of the history of European forms of this custom would be advisable.”