1. Anderson , M.C 2004 Executive briefing: The business impact of leadership coaching at a professional services firm http://www.google.de/search?sourceid=chromeandie=UTF-8andq=http://www.cylient.+com/images/pdfs/MetrixGlobalROIofCoachingProfSvsExecBrief.pdf.+Anderson
2. Estimating return on leadership development investment;Avolio;The Leadership Quarterly,2010
3. A meta-analytic review of leadership impact research: Experimental and quasi-experimental studies;Avolio;Leadership Quarterly,2009