Japanese Ministry of Internal Affairs and Communications: Kinou Bunseki (Functional Analysis) DMM, http://www.soumu.go.jp/denshijiti/system_tebiki/hyouki/gyomu/2a-2-dmm.html.
Department of Defense: Department of Defense Handbook Work Breakdown Structure, 1993.
Abell F: Defining the Business, The Starting Point of Strategic Planning, Prentice Hall, 1980.