ROYAL, Mark - AGNEW, Thomas George Arnold. The enemy of engagement [elektronický zdroj]. New York : American Management Association, c2012. 1 online resource (viii, 230 s.). Available on Internet: <http://search.ebscohost.com/login.aspx?direct=true&scope=site&db=nlebk&db=nlabk&AN=392642> ISBN 0814417965.