Authority Vs Power

There is a fine line of difference between power and authority. Do you agree ? 

Power is the possession of authority, control, or influence by which a person influences the actions of others, either by direct authority or by some other, more intangible means. A prime source of power is the possession of knowledge. A person with knowledge is oftentimes able to use that knowledge to directly or indirectly influence the actions of others. The authority of knowledge is often independent of levels or positions. Power can reinforce authority, and authority is one of the primary sources of power.
Power and authority are separate but related concepts. A manager in an organization has authority if he or she has the right to direct the activities of others and expect them to respond with appropriate actions to attain organizational purposes. Authority most often comes from the duties and responsibilities delegated to a position holder in a bureaucratic structure. A company president can order a product design change, for instance, or a police officer has the authority to arrest an offender of the law.
JamesHunter writes in TheServant (pp.29-34) that "If leadership is about influencing others, how do we go about developing that influence with people? How do we get people to do our will? How do we get their ideas, commitment, creativity, and excellence, which are by definition voluntary gifts? To better understand how one develops this type of influence, it is critical to understand the difference between power and authority
However, Authority cannot be bought or sold, given or taken away. Authority is about who you are as a person, your character, and the influence you've built with people it is one's expression of one's self, which is treated thoroughly by Warren Bennis in OnBecomingaLeader. Power erodes relationships. You can get a few seasons out of power, even accomplish some things, but over time power can be very damaging to relationships. ... there are times when we must exercise power ... in firing a bad employee

Do you then agree that LeaderShip leads by authority and not by power.