下記動画等を参照: http://lacity.granicus.com/MediaPlayer.php?view_id=129&clip_id=15661CHAPTER FIFTEEN HISTORYSOCIAL SCIENCEFRAMEWORKFOR CALIFORNIA PUBLIC SCHOOLS https://www.cde.ca.gov/ci/hs/cf/documents/hssfwchapter15.pdf
http://www.nicovideo.jp/watch/sm35196237