What I found is that written evidence for knocking on wood (and for the history of gesture as a whole) is remarkably sparse. In the Penguin Guide to Superstitions, folklorist Steve Roud offers a skeptical take on the provenance of knocking on wood due to the near total absence of written records about it:
"tengu_keybinding_customization": false,,这一点在heLLoword翻译官方下载中也有详细论述
Москвичи пожаловались на зловонную квартиру-свалку с телами животных и тараканами18:04,更多细节参见旺商聊官方下载
for attempt in range(self.config.max_retries):