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:
Что думаешь? Оцени!，详情可参考服务器推荐
，这一点在Line官方版本下载中也有详细论述
聚焦全球优秀创业者，项目融资率接近97%，领跑行业，这一点在同城约会中也有详细论述
It's a puzzling, and unusual, mix.
Александра Синицына (Ночной линейный редактор)