Density of states for Bose-Einstein condensation in harmonic oscillator   potentials
  We discuss how it is possible to obtain a reliable approximation for the density of states for a system of particles in an anisotropic harmonic oscillator potential. A direct application of the result to study Bose-Einstein condensation of atomic gases in a potential trap can be given. In contrast to a previous study, our method involves only analytic calculations. 
Klaus Kirsten and David J. Toms