@article{702182,
title = {Nonlinear differential systems of the third and fourth order},
booktitle = {Differential Equations and Their Applications},
series = {GDML\_Books},
publisher = {Publishing House of the Czechoslovak Academy of Sciences},
address = {Prague},
year = {1963},
pages = {143-165},
mrnumber = {MR0168858},
zbl = {0132.31803},
url = {http://dml.mathdoc.fr/item/702182}
}
Sansone, G. Nonlinear differential systems of the third and fourth order, dans Differential Equations and Their Applications, GDML_Books, (1963), pp. 143-165. http://gdmltest.u-ga.fr/item/702182/