Pii: S1007-5704(02)00018-7

In a previous paper [Chaos Solitons Fract. 14(2) (2002) 173], the authors investigated the dynamics of the equation: dx dt2 þ ðd þ cos tÞxþ Ax " þ Bx dx dt þ Cx dx dt 2 þ D dx dt 3# 1⁄4 0 We used the method of averaging in the neighborhood of the 2:1 resonance in the limit of small forcing and small nonlinearity. We found that a degenerate bifurcation point occurs in the resulting slow flow and some of the bifurcations near this point were looked at. In this work we present additional results concerning the bifurcations around this point using analytic techniques and AUTO. An analytic approximation for a heteroclinic bifurcation curve is obtained. Additional results on the bifurcations of periodic orbits in the slow flow are also presented. 2002 Published by Elsevier Science B.V. PACS: 05.45