On the paper by M. Valluri and D. Merritt "Orbital Instability and   Relaxation in Stellar Systems"
  Some points related to the exponential instability of N-body gravitating systems and which are misinterpreted in various papers are clarified. Exponential instability is a phenomenon essentially responsible for the relaxation, evolutionary, morphological and other properties of certain type of galaxies and star clusters. 
V.G.Gurzadyan