Sanders, J.A & Verhulst, F <br/><br/>
Averaging methods in nonlinear dynamical systems 
J.A. Sanders & F. Verhulst 
 - New York  Springer  1985 
 - x  247 
 - Applied mathematical sciences 59 .
<br/><br/><label>ISBN: </label>3540962298 
<br/><br/><label>Dewey Class. No.: </label>12.01+11.07  / SAND