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 ...