Comparisons of short-term efficacy between individual and group cognitive behavioral therapy for primary insomnia. - Yamadera, Wataru; Sato, Miki; Harada, Daisuke; Iwashita, Masayuki; Aoki, Ryo; Obuchi, Keita; Ozone, Motohiro; Itoh, Hiroshi; Nakayama, Kazuhiko (Sleep & Biological Rhythms, 2013)