@book{ BA69418978,
  author    = "Gattegno, Caleb",
  title     = "Awareness of the awareness",
  publisher = "Educaitonal Solutions",
  year      = "1977",
  series    = "The science of education / Caleb Gattegno",
  number    = "ch. 2",
  URL       = "https://ci.nii.ac.jp/ncid/BA69418978"
}