David Cottrell, Mark C. Layton (2002). “The Manager's Coaching Handbook: A Practical Guide to Improving Employee Performance”, p.1, The Walk The Talk Company
David Cottrell, Mark C. Layton (2002). “The Manager's Coaching Handbook: A Practical Guide to Improving Employee Performance”, p.39, The Walk The Talk Company
David Cottrell, Eric Lee Harvey (2004). “Leadership Courage: Leadership Strategies for Individual and Organizational Success”, p.17, The Walk The Talk Company