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:
Москвичей предупредили о резком похолодании09:45
，这一点在雷电模拟器官方版本下载中也有详细论述
Have you experienced the new routing speed?
Мерц резко сменил риторику во время встречи в Китае09:25
。业内人士推荐safew官方版本下载作为进阶阅读
'Scream 7' review: Kevin Williamson makes Ghostface fun again
Что думаешь? Оцени!，详情可参考heLLoword翻译官方下载