代表作
auasiperiodic solutions of duffing's equations, nonlinear analysis,33(1998),645-655.
boundedness in nonlinear oscillations at resonance. j.d.e.153(1999),142-174
boundedness of solutions ... j.d.e145(1998),119-144
boundedness of solutions of nonlinear differential equations, j.d.e.144(1998),66-98
the stability of the equilibrium of reversible systems, trans.a.m.s.351(1999),515-531
