The occurrence of a triple -1 resonance in the standard singularity   analysis
  Any careful singularity analysis of the Mixmaster Universe uncovers the instance of a triple -1 resonance. The Mixmaster Universe does not exhibit a closed-form solution and so a correct interpretation of the meaning of the triple -1 resonance is difficult. We provide a system of differential equations for which both a closed-form solution and a triple -1 resonance exist. 
K. Andriopoulos and P.G.L. Leach