Willingham, R. (1997). The people principle: A revolutionary redefinition of leadership. St. Martins press.
Citazione stile Chigago Style (17a edizione)Willingham, Ron. The People Principle: A Revolutionary Redefinition of Leadership. New York: St. Martins press, 1997.
Citatione MLA (9a ed.)Willingham, Ron. The People Principle: A Revolutionary Redefinition of Leadership. St. Martins press, 1997.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.