@article{COCV_2020__26_1_A7_0,
     author = {Wei, Hui and Ji, Shuguan},
     title = {Infinitely many periodic solutions for a semilinear wave equation with \protect\emph{x}-dependent coefficients},
     journal = {ESAIM: Control, Optimisation and Calculus of Variations},
     publisher = {EDP-Sciences},
     volume = {26},
     year = {2020},
     doi = {10.1051/cocv/2019007},
     mrnumber = {4062158},
     zbl = {1439.35341},
     language = {en},
     url = {http://archive.numdam.org/articles/10.1051/cocv/2019007/}
}