One of the most influential theories of power comes from the work of French and Raven, who attempted to determine the sources of power used by leaders to influence others. French and Raven identified five sources of power that can be grouped into two categories: organizational power (legitimate, rewarding, coercive) and personal power (expert and referent). Personal sources of power are more strongly related to employees' job satisfaction, organizational commitment, and job performance than are organizational sources of power. “However, different energy sources should not be considered completely separate from each other. Sometimes leaders use sources of power together in varying combinations depending on the situation. A new concept of power, called “empowerment,” has become a major strategy for improving work.