The problem of the periodic motions of a system with a small parameter
is solved. The non-rough cases, when the problem cannot be solved by
a generating system obtained for a zero value of the small parameter,
are investigated. Lyapunov's idea of using a new generating system whi
ch already contains the small parameter is systematically developed. S
ystems of general form, inverse systems and systems close to inverse a
re investigated. (C) 1998 Elsevier Science Ltd. All rights reserved.