Another current trend in self-leadership research concerns self-leadership contingency factors. Although proponents have generally encouraged the use of self-leadership strategies across a wide variety of situations, some researchers have questioned whether self-leadership should be encouraged across all types of situations. For example, Markham and Markham have raised the issue as to whether self-leadership is "a universally applicable theory that will work with all employees under all circumstances" or "a contingency theory that best fits certain boundary conditions”. As a matter of fact, self-leadership theorists have often admitted that encouraging follower self-leadership may not be universally appropriate. For instance, Manz and Sims have stated that "it is naive to assume that relying on self-leadership is always appropriate [....] several important situational factors influence the appropriateness of attempts to develop self-leadership in followers.