@article{10_4153_CMB_1968_092_2,
     author = {Burton, T.A.},
     title = {Periodic {Solutions} by {Picard's} {Approximations}},
     journal = {Canadian mathematical bulletin},
     pages = {743--745},
     year = {1968},
     volume = {11},
     number = {5},
     doi = {10.4153/CMB-1968-092-2},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1968-092-2/}
}