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:
│ VMM (User-Space) │ ◄── DEVICE EMULATION
技术支持：陈晓龙 叶伟豪 肖杰，这一点在夫子中也有详细论述
Трамп высказался о непростом решении по Ирану09:14
Цены на нефть взлетели до максимума за полгода17:55