@article{EJDE_2014__2014__a178,
     author = {Li,  Qiang and Li,  Yongxiang},
     title = {Existence and multiplicity of positive periodic solutions for second-order functional differential equations with infinite delay},
     journal = {Electronic journal of differential equations},
     year = {2014},
     volume = {2014},
     zbl = {1290.34070},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2014__2014__a178/}
}