Ballmer, S. (2007) Steve Ballmer Speaks Passionately about Microsoft, Leadership ... And Passion; taken from http://knowledge.wharton.upenn.edu
Bolden, R., Gosling, J., Marturano, A. And Dennison, P (2003) A review of leadership theory and competency frameworks - Edited Version of a Report for Chase Consulting and the Management Standards Centre, Exeter: University of Exeter.
Chemers M. (1997) An integrative theory of leadership. Mahwah, USA: Lawrence Erlbaum Associates Inc., Publishers. Taken from http://en.wikipedia.org/wiki/Leadership#cite_note-1
Covey, S. (1992) Principle Centered Leadership. Fireside/Simon & Schuster: New York.