The Bianchi Ix (MIXMASTER) Cosmological Model is Not Integrable
  The perturbation of an exact solution exhibits a movable transcendental essential singularity, thus proving the nonintegrability. Then, all possible exact particular solutions which may be written in closed form are isolated with the perturbative Painlev\'e test; this proves the inexistence of any vacuum solution other than the three known ones. 
A.~Latifi (Universit\'e libre de Bruxelles), M.~Musette (Vrije   Universiteit Brussel) and R.~Conte (CEA, Centre d'\'etudes ...