@article{EJDE_2006__2006__a34,
     author = {Zhu,  Jianmin and Li,  Zhixiang and Liu,  Yicheng},
     title = {Stable time periodic solutions for damped {sine-Gordon} equations},
     journal = {Electronic journal of differential equations},
     year = {2006},
     volume = {2006},
     zbl = {1115.35118},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2006__2006__a34/}
}