@article{10_21136_AM_2020_0006_19,
     author = {Li, Zhanyong and Liu, Qihuai and Zhang, Kelei},
     title = {Periodic solutions of nonlinear differential systems by the method of averaging},
     journal = {Applications of Mathematics},
     pages = {511--542},
     publisher = {mathdoc},
     volume = {65},
     number = {4},
     year = {2020},
     doi = {10.21136/AM.2020.0006-19},
     mrnumber = {4134145},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/AM.2020.0006-19/}
}