Willingham, R. (1997). The people principle: A revolutionary redefinition of leadership. St. Martins press.
Lua i Stíl Chicago (17ú heag.)Willingham, Ron. The People Principle: A Revolutionary Redefinition of Leadership. New York: St. Martins press, 1997.
Lua MLA (9ú heag.)Willingham, Ron. The People Principle: A Revolutionary Redefinition of Leadership. St. Martins press, 1997.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.