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.”
Source: Computational Materials Science, Volume 267。关于这个话题，服务器推荐提供了深入分析
，这一点在雷电模拟器官方版本下载中也有详细论述
Россия обратилась с требованием к ВеликобританииКелин: Россия требует, чтобы Британия отказалась от планов передачи ЯО Украине，更多细节参见爱思助手下载最新版本
In an internal memo cutting the Pentagon’s long list of priority technologies down to six, he wrote that the previous list “did not provide the focus that the threat environment of today requires,” and declared that “in alignment with President Trump’s Artificial Intelligence (AI) Action Plan, the Department of War must become an ‘AI‑First’ organization.”