@article{EJDE_2012__2012__a71,
     author = {Payne, Victor F. and Tejumola, Haroon Oladipo},
     title = {Existence and nonexistence of periodic solutions of $n$-vector differential equations of orders six and seven},
     journal = {Electronic Journal of Differential Equations},
     publisher = {mathdoc},
     volume = {2012},
     year = {2012},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/EJDE_2012__2012__a71/}
}