Electronic Journal of Differential Equations,
Vol. 2007(2007), No. 119, pp. 1-23.

Title: Centres and limit cycles for an extended Kukles system

Authors: Joe M. Hill     (Aberystwyth Univ., Wales  UK)
         Noel G. Lloyd   (Aberystwyth Univ., Wales  UK)
	 Jane M. Pearson (Aberystwyth Univ., Wales  UK)

Abstract: 
 We present conditions for the origin to be a centre for a class
 of cubic systems.  Some of the centre conditions are determined
 by finding complicated invariant functions.  We also investigate
 the coexistence of fine foci and the simultaneous bifurcation of
 limit cycles from them.
 
Submitted August 10, 2007. Published September 06, 2007.
Math Subject Classifications: 34C07, 37G15.
Key Words: Nonlinear differential equations; invariant curves; 
           limit cycles.