Erratum to: A randomized double-blind multi-center trial of hydrogen water for Parkinson's disease: protocol and baseline characteristics. Issue 1 (December 2017) - Yoritaka, Asako; Abe, Takashi; Ohtsuka, Chigumi; Maeda, Tetsuya; Hirayama, Masaaki; Watanabe, Hirohisa; Saiki, Hidemoto; Oyama, Genko; Fukae, Jiro; Shimo, Yasushi; Hatano, Taku; Kawajiri, Sumihiro; et al.