On a Generalized D-Dimensional Oscillator: Interbasis Expansions
  This article deals with nonrelativistic study of a D-dimensional superintegrable system, which generalizes the ordinary isotropic oscillator system. The coefficients for the expansion between the hyperspherical and Cartesian bases (transition matrix), and vice-versa, are found in terms of the SU(2) Clebsch--Gordan coefficients analytically continued to real values of their arguments. The diagram method, which allow one to construct a transition matrix for arbitrary dimension, is developed. 
Ye.M.Hakobyan, G.S.Pogosyan, A.N.Sissakian