Unbounded solutions of a class of planar systems

In this paper, the unbounded solutions for the following nonlinear planar system: is discussed, where <f>a±,b±</f> are positive constants satisfying <f>x±=max{±x,0}</f>, <f>y±=max{±y,0}</f>, <f>ω∈R+&z.drule;Q</f>, <f>f(t),g(t)∈L∞[0,2π]</f> are <f>2π</f>-periodic functions. [Copyright &y& Elsevier]