@article{PORMA_2005__62_1_52221,
     author = {Amster, P. and de N\'apoli, P. and Mariani, M.C.},
     title = {Periodic solutions of a resonant higher order equation.},
     journal = {Portugaliae mathematica},
     pages = {13--24},
     publisher = {mathdoc},
     volume = {62},
     number = {1},
     year = {2005},
     zbl = {1084.34043},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_2005__62_1_52221/}
}