\input zb-basic
\input zb-ioport
\iteman{io-port 50275448}
\itemau{Zhang, Hui-Li}
\itemti{Application of He's amplitude-frequency formulation to a nonlinear oscillator with discontinuity}
\itemso{Computers & Mathematics with Applications 58, No. 11-12, 2197-2198 (2009).}
\itemcc{}
\itemut{}
\itemli{doi:10.1016/j.camwa.2009.03.018}
\end