@article{MOMA_1964__68_177237,
     author = {C.M. Petty and G. Leitmann},
     title = {A {Boundedness} {Theorem} for a {Nonlinear,} {Nonautonomous} {System.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {46--51},
     publisher = {mathdoc},
     volume = {68},
     year = {1964},
     zbl = {0122.09305},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1964__68_177237/}
}