The hierarchic systems with fast rotating phases are the most popular among asymptotic hierarchic methods in different branches of applied physics for two reasons. First, it is because the physical models that can be described by such equations are in widespread use. Second, it is because-as is mentioned in Chapter 5-analytical algorithms of asymptotic integration of this type of system can be constructed without excessive dif£culty. Taking this into consideration, we will pay special attention to this in later chapters when studying systems with fast rotating phases.