@article{Duval:2014,
  author  = "G. Duval and A. Maciejewski",
  title   = "Integrability of Hamiltonian systems with homogeneous potentials od degrees [...]2. An application of order variational equations",
  journal = "Discrete and Continuous Dynamical Systems - Series A",
  volume  = "Vol. 34",
  number  = "no. 11",
  pages   = "4589--4615",
  year    = "2014",
}